Polishing apparatus

ABSTRACT

A polishing apparatus polishes a workpiece such as a semiconductor wafer. The polishing apparatus comprises a table ( 30 ) which makes a motion, a base ( 20 ) placed on the table, a polishing tool ( 10 ) fixed to the base and having a polishing surface for polishing a surface of the workpiece (W), a plurality of transmission members ( 41 ) provided along a circumferential direction of the table, and a plurality of holes ( 22 ) formed in the base. The transmission members are inserted into the holes, respectively, for transmitting the motion of the table to the base.

TECHNICAL FIELD

The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having a structure which can mount a polishing tool such as a fixed abrasive on a polishing table reliably.

BACKGROUND ART

As semiconductor devices have become more highly integrated in recent years, circuit interconnections become finer and dimensions of integrated devices become smaller. Therefore, there has been required a process for polishing and removing a film formed on a surface of a semiconductor wafer to planarize the surface of the semiconductor wafer. A polishing apparatus for performing chemical mechanical polishing (CMP) has been used for planarizing the surface of the semiconductor wafer.

This type of polishing apparatus comprises a polishing table having a polishing cloth (polishing pad) attached thereon, and a top ring for holding a workpiece, to be polished, such as a semiconductor wafer. The workpiece is disposed between the polishing pad and the top ring and pressed against the polishing pad under a certain pressure by the top ring while the polishing table and the top ring are being rotated. The workpiece is polished to a flat mirror finish while a polishing liquid (slurry) is being supplied onto the polishing pad.

As described above, the chemical mechanical polishing (CMP) process has been employed in a semiconductor device fabrication process to planarize irregularities on a surface of a semiconductor wafer which are formed in a deposition process of an insulating film or an interconnection metal film, for example. According to the chemical mechanical polishing process, a workpiece such as a semiconductor wafer is held by the top ring and pressed against a polishing pad made of hard polyurethane foam or the like. The workpiece is polished to a flat mirror finish while a polishing liquid (slurry) is being supplied onto the polishing pad. The polishing pad is attached on a polishing table by an adhesive tape or the like.

Depending on the type of films to be polished or slurry to be used, the polishing rate of a wafer or the uniformity of the polishing rates within a wafer can be improved by providing grooves of a lattice-like pattern or concentric grooves in the surface of the polishing pad. Once the adhesive tape which has been used to bond the polishing pad to the polishing table is peeled off, it cannot be reused because its adhesive strength is lowered. When the polishing pad is directly attached to the polishing table, the expensive polishing pad needs to be discarded each time the polishing pad is replaced according to the type of films to be polished or slurry to be used. Therefore, attempts have been made to reduce the cost of the polishing pads. Specifically, the polishing pad is bonded to a polishing pad attachment typified by a base which is made of a material having a high mechanical strength, such as metal or engineering plastics, and the base is fixed to the polishing table with a mechanism that allows the base to easily be attached to and detached from the polishing table. In such attempts, the polishing pad can be replaced many times.

In the chemical mechanical polishing process using a polishing liquid (slurry) as described above, a workpiece is polished while a polishing liquid containing a large amount of abrasive particles is being supplied onto a relatively soft polishing pad. Therefore, the problem of pattern dependence arises. The pattern dependence means that gentle irregularities are formed on a surface of a semiconductor wafer after the polishing process due to irregularities on the surface of the semiconductor wafer that has existed before the polishing process, thus making it difficult to planarize the surface of the semiconductor wafer to a completely flat surface. Specifically, the polishing rate is higher for irregularities having small pitches and is lower for irregularities having large pitches, and the existence of areas of the higher polishing rate and areas of the lower polishing rate causes gentle irregularities to be formed on the surface of the semiconductor wafer.

It has also been practiced to polish a semiconductor wafer with use of a fixed abrasive (grindstone) which comprises abrasive particles of cerium oxide (CeO₂), TiO₂, SiO₂, Al₂O₃, ZrO₂, MnO₂, Mn₂O₃, or the like fixed by a binder such as a thermoplastic resin or a thermosetting resin (phenolic resin), instead of a polishing pad made of hard polyurethane foam or the like. The polishing process with use of the fixed abrasive is advantageous in that the polishing material, i.e., the fixed abrasive, is harder than the polishing pad used in the conventional CMP process, and tends to polish convexities of the irregularities more than concavities thereof, for thereby achieving a higher absolute level of planarity. Depending on the composition of the fixed abrasive, the fixed abrasive provides a self-stop function which considerably lowers the polishing rate and practically stops the polishing process when the convexities of the irregularities are polished to a flat surface. The polishing process with use of the fixed abrasive is also advantageous in that the environmental load can be reduced because of no use of a suspension liquid (slurry) containing a large amount of abrasive particles. Further, while most of the abrasive particles supplied to the polishing pad are discharged without contributing to the polishing process, the fixed abrasive polishes the workpiece by loosening a minimum amount of abrasive particles on the polishing surface with a dressing (conditioning) process. Therefore, the fixed abrasive has been expected to lower the cost and reduce the environmental load.

Such a hard fixed abrasive is more liable to crack under external shocks than the polishing pad made of hard polyurethane foam or the like. Therefore, more care should be given to handling the fixed abrasive. The fixed abrasive is heavy and difficult to be attached to the polishing table by an adhesive tape unlike the polishing pad. In order to protect the fixed abrasive and to facilitate the attachment of the fixed abrasive to the apparatus, the fixed abrasive is fixed to a fixed abrasive attachment (base) made of a material having a high mechanical strength, such as metal or engineering plastics, by an adhesive or the like. The base is fixed to the polishing table with a mechanism that allows the base to easily be attached to and detached from the polishing table.

Generally, the processing temperature rises during polishing due to the frictional heat produced between the workpiece and the polishing tool and the heat of the chemical reaction between chemical substances in the polishing liquid and the film being polished. If the temperature increases rapidly or drastically, then the base or the polishing tool is thermally expanded and deformed to such an extent that the polishing surface loses its planarity. FIGS. 1A and 1B schematically show the manner in which the polishing surface loses its planarity. As shown in FIG. 1A, a polishing tool 903 comprising a fixed abrasive is mounted on a polishing table 901 with a base (polishing tool attachment) 902 interposed therebetween. When the temperature increases rapidly or drastically, the base 902 and the polishing tool 903 are thermally expanded and deformed to such an extent that the polishing surface on the polishing tool 903 loses its planarity.

When the base 902 and the polishing tool 903 are deformed to such an extent that the polishing surface on the polishing tool 903 loses its planarity, the processing pressure (polishing pressure) periodically varies, i.e., components in the polishing apparatus vibrate, due to the lack of the planarity of the polishing surface. The vibration promotes the metal fatigue of components in the polishing apparatus. Therefore, the components in the polishing apparatus are frequently damaged, so that the maintenance cost of the polishing apparatus increases. Furthermore, when the processing pressure excessively increases by the vibration, a scratch may be caused on the workpiece such as a semiconductor wafer, thus resulting in a reduction in yield.

If the polishing tool 903 and the base 902 have largely different coefficients of thermal expansion from each other, then the polishing tool 903 and the base 902 are so distorted relatively to each other that the adhesive layer is broken by a produced shearing force, thus exfoliating the polishing tool 903 from the base 902.

Further, since the fixed abrasive has a low mechanical strength, it is difficult to mount the fixed abrasive directly on a conventional polishing table. Therefore, the fixed abrasive needs to be attached to a cartridge table (base table) having a sufficient strength. However, the cartridge table having a high strength and the fixed abrasive comprising fixed abrasive particles are heavy. Thus, the cartridge table having the fixed abrasive attached thereto is so heavy that the fixed abrasive is difficult to be moved and cannot be handled with ease. As a result, it is difficult to position the fixed abrasive with respect to the main table. Furthermore, it is very difficult to accomplish attachment of the heavy cartridge table on the main table.

Consequently, a fixed abrasive for polishing a semiconductor wafer has been composed of a base table which is made of a very light material and a thin fixed abrasive. Thus, it is practically difficult to increase the thickness of the fixed abrasive so as to prolong the service life thereof.

DISCLOSURE OF INVENTION

The present invention has been made in view of the above drawbacks. It is a first object of the present invention to provide a polishing apparatus having a structure which can minimize a distortion of a polishing surface due to thermal expansion of a polishing tool (a polishing pad, a fixed abrasive, or the like) and a base, and can prevent the polishing tool from being detached from the base.

A second object of the present invention is to provide a polishing tool assembly and a polishing apparatus having such a polishing tool assembly which can prevent a portion of a peripheral edge of a workpiece, such as a semiconductor wafer from being excessively polished, and can uniformly process the workpiece.

A third object of the present invention is to provide a polishing apparatus which can prolong the service life of a polishing tool, facilitate handling of a polishing tool, and improve the safety of the operator, and a method of assembling a cartridge table having a polishing tool on a main table.

According to a first aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table; a base placed on the table; and a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; wherein the base has at least a portion which is not fixed to the table for allowing the base to be deformed through the portion.

Since the base has at least a portion which is not fixed to the table, when the base is deformed due to thermal expansion, such a deformation is allowed to occur at the portion which is not fixed to the table. Thus, the polishing surface of the polishing tool can be kept flat.

According to a preferred aspect of the present invention, the polishing apparatus further comprises a fixing member for fixing the base to the table.

Since the polishing apparatus has the fixing member for fixing the base to the table, the base with the polishing tool fixed thereto can easily be mounted on and dismounted from the table.

According to a preferred aspect of the present invention, the polishing apparatus further comprises a transmission member provided on the table at a position where the base is not fixed to the table; wherein the table makes a motion, and the motion of the table is transmitted to the base through the transmission member.

Since the transmission member is provided for transmitting the motion of the table to the base at a position where the base is not fixed to the table, the deformation of the base and the polishing tool due to thermal expansion is allowed to occur at the portion of the base which is not fixed to the table. At the same time, the motion of the table can be transmitted to the base through the transmission member.

According to a preferred aspect of the present invention, the base comprises a plurality of base segments.

In the case where the polishing tool and the base are large in size, since the base comprises a plurality of base segments, the base can easily be handled when the base is placed on and displaced from the table.

According to a preferred aspect of the present invention, the polishing tool comprises a fixed abrasive.

In the case where the polishing tool comprises the fixed abrasive as described above, the present invention can offer the following advantages: A flatness of the polishing surface can be maintained, the base can easily be attached to or detached from the table, the deformation of the polishing tool due to thermal expansion can be allowed to occur, and the motion of the table can be transmitted to the base.

According to a preferred aspect of the present invention, the base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times a coefficient of linear expansion of the polishing tool.

Since the base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times the coefficient of linear expansion of the polishing tool, the polishing tool and the base are deformed substantially equally to each other when thermal expansion occurs due to an increase in temperature caused by the polishing process. Therefore, shearing forces acting on the adhesive layer between the polishing tool and the base can be reduced, thus preventing the polishing tool from being detached from the base.

According to another aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table; a base placed on the table and having an annular shape; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; and a fixing member for fixing the base to the table; wherein an inner circumferential portion of the base is fixed to the table by the fixing member and an outer circumferential portion of the base is not fixed to the table so as to allow the base to be deformed radially outwardly.

According to a preferred aspect of the present invention, the base comprises a plurality of base segments having a fan shape.

According to a preferred aspect of the present invention, a polishing apparatus further comprises a plurality of transmission members provided along a circumferential direction of the table; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base, the transmission members being inserted into the holes, respectively, for transmitting the motion of the table to the base.

According to still another aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table; a base placed on the table and having an annular shape; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; and a fixing member for fixing the base to the table; wherein the base comprises a plurality of base segments, the polishing tool comprises a plurality of polishing tool segments which are fixed to the plurality of base segments, respectively, and an outer circumferential portion of the base is fixed to the table by the fixing member and an inner circumferential portion of the base is not fixed to the table so as to allow the base to be deformed radially inwardly.

According to a preferred aspect of the present invention, each of the base segments has a fan shape.

According to a preferred aspect of the present invention, a polishing apparatus further comprises a plurality of transmission members provided along a circumferential direction of the table; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base, the transmission members being inserted into the holes, respectively, for transmitting the motion of the table to the base. The elongate shape includes, for example, an elliptical shape and a rectangular shape.

According to still another aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table which makes a motion; a base placed on the table; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; a plurality of transmission members provided along a circumferential direction of the table; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base, the transmission members being inserted into the holes, respectively, for transmitting the motion of the table to the base.

According to-still another aspect of the present invention, there is provided a polishing tool assembly for polishing a workpiece, comprising: a base positionable on a table; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece, the polishing tool comprising a fixed abrasive; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base; wherein the holes are arranged to allow a plurality of transmission members provided along a circumferential direction of the table to be inserted therein when the polishing tool assembly is mounted on the table.

In order to achieve the second object, according to a second aspect of the present invention, there is provided a polishing tool assembly for polishing a workpiece, comprising: a plurality of polishing tool segments having a polishing surface for polishing a surface of the workpiece; and a polishing tool attachment for holding the polishing tool segments thereon in such a state that the circumferentially adjacent polishing tool segments are held in close contact with each other.

According to the present invention, the circumferentially adjacent polishing tool segments are held in close contact with each other. Therefore, when the workpiece is brought into sliding contact with the polishing surface across the polishing tool segments, a pressure acting on the surface of the workpiece does not change, and hence the surface of the workpiece can uniformly be processed. Since the polishing tool assembly comprises a plurality of polishing tool segments, each of the polishing tool segments can be made small in size, and the polishing tool assembly can be manufactured with small-scale equipments for forming the polishing tool assembly. Thus, initial investments and the manufacturing-cost of the polishing tool assembly can be reduced.

According to a preferred aspect of the present invention, the polishing tool segment comprises a fixed abrasive having abrasive particles fixed by a binder.

According to a preferred aspect of the present invention, each of the polishing tool segments is in a sectorial or fan-shaped form, and the circumferentially adjacent polishing tool segments are held in close contact with each other to form a disk or cylindrical shape as a whole.

Thus, each of the polishing tool segments is in a sectorial or fan-shaped form, and the circumferentially adjacent polishing tool segments are held in close contact with each other. Therefore, even though the polishing tool assembly comprises a plurality of polishing tool segments, the polishing tool segments can easily be positioned with respect to each other so as to form a disk or cylindrical shape as a whole when the polishing tool segments are mounted on the polishing tool attachment. Accordingly, the polishing tool can easily be assembled in a simple process.

According to a preferred aspect of the present invention, the polishing tool segments are mounted on the polishing tool attachment in such a state that the polishing tool segments are positioned with use of a positioning member mounted around the outer circumferential edges of the polishing tool segments.

According to a preferred aspect of the present invention, the polishing tool attachment has an outside diameter larger than the polishing tool segments. This arrangement can provide an attachment portion at a peripheral edge of the polishing tool attachment for attaching the polishing tool attachment to a polishing table.

According to a preferred aspect of the present invention, the polishing tool segments are mounted on a single polishing tool attachment.

According to a preferred aspect of the present invention, the polishing tool attachment is divided into a plurality of attachment segments so as to correspond to the polishing tool segments, and the polishing tool segments are mounted on the respective attachment segments.

In a CMP apparatus for polishing a 12-inch wafer, a polishing tool (fixed abrasive) has a diameter ranging from 700 to 800 mm and is heavy. Therefore, the polishing tool cannot be handled with ease at the time of replacement thereof. According to the present invention, the polishing tool segments are mounted on the attachment segments divided so as to correspond to the respective polishing tool segments. Therefore, even if the polishing tool assembly has a large diameter and is heavy, the polishing tool segments can easily be handled together with the respective attachment segments. Accordingly, a smaller space is required in a clean room for replacing the polishing tool assembly. Further, each of the polishing tool segments is so light in weight that it can easily be handled without any special device such as a crane or a lifter. As a result, the polishing tool assembly can be handled with ease in the clean room.

In order to achieve the second object, according to a third aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a workpiece holding device for holding the workpiece; the aforementioned polishing tool assembly; and a polishing table on which the polishing tool is mounted.

In order to achieve the third object, according to a fourth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which the polishing tool is mounted; a main table disposed so as to face a reverse surface of the cartridge table and having a support surface for supporting the cartridge table thereon; a moving mechanism mounted on the reverse surface of the cartridge table or the support surface of the main table for facilitating movement of the cartridge table along the main table; and a positioning member for positioning the cartridge table with respect to the main table. The support surface of the main table may support the cartridge table directly or may support the cartridge table through another member.

According to the present invention, as shown in, for example, FIGS. 15A and 15B, and 19A and 19B, since the moving mechanism 322 and the positioning member 333 are provided, the cartridge table 316 can easily be moved on the main table 305 by the moving mechanism 322, and the cartridge table 316 can easily be positioned on the main table 305 by the positioning member 333. Therefore, the handling capability of the polishing tool 315 can be increased, and the safety of the operator can be increased. Further, the thickness of the polishing tool 315 can be increased, and hence the service life of the polishing tool 315 can be prolonged.

According to a preferred aspect of the present invention, the moving mechanism comprises a rolling element which rolls on the support surface of the main table, or the reverse surface of the cartridge table.

According to a preferred aspect of the present invention, the positioning member comprises a recess formed in the support surface of the main table or the reverse surface of the cartridge table for accommodating the rolling element.

As shown in FIG. 18A, the positioning member 333 typically comprises a recess formed in the reverse surface 316B or the support surface 305A on which the moving mechanism 322 is not mounted, and the moving mechanism 322 such as a rolling element which moves on the reverse surface 316B enters the recess for thereby positioning the cartridge table 316 with respect to the main table 305.

According to a preferred aspect of the present invention, a polishing apparatus further comprises a fastening member for securing the cartridge table to the main table.

According to a preferred aspect of the present invention, the moving mechanism is disposed in point symmetry with respect to a center of the surface on which the moving mechanism is mounted.

With the above arrangement, as shown in, for example, FIG. 17, the moving mechanism 322 is disposed in point symmetry with respect to the center C1 of the attachment surface 316B on which the moving mechanism is mounted, and hence the cartridge table 316 on the main table 305 can take at least two angular attitudes (or postures) about a line which passes through the center C1 and is perpendicular to the attachment surface 316B. The moving mechanism 322 may be positioned at an equal distance R from the center C1 of the attachment surface 316B. The number of attitudes that the cartridge table 316 can take can be increased, allowing the cartridge table 316 to be easily positioned on the main table 305.

According to a preferred aspect of the present invention, the polishing tool comprises a fixed abrasive.

In order to achieve the third object, according to a fifth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which the polishing tool is mounted; a main table disposed so as to face a reverse surface of the cartridge table and having a support surface for supporting the cartridge table thereon; a rolling element mounted on the reverse surface of the cartridge table or the support surface of the main table and rolling on the support surface of the main table or the reverse surface of the cartridge table; and a recess formed in the support surface of the main table or the reverse surface of the cartridge table for accommodating the rolling element.

In order to achieve the third object, according to a sixth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which the polishing tool is mounted; and a main table disposed so as to face a reverse surface of the cartridge table and having a support surface for supporting the cartridge table thereon; wherein the cartridge table is coupled to a carrier device for carrying the cartridge table onto the support surface of the main table when the cartridge table is to be mounted on the main table and carrying the cartridge table upwardly above the support surface when the cartridge table is dismounted from the main table.

According to the present invention, as shown in, for example, FIGS. 15A and 15B, 21 and 27, since the cartridge table 316 is coupled to the carrier device 501, the cartridge table 316 can be carried onto the support surface 454A of the main table 454 when installed and can be carried upwardly from the support surface 454A when dismounted. Therefore, the handling capability of the heavy polishing tool 315 can be increased, and the safety of the operator can be increased.

According to a preferred aspect of the present invention, a polishing apparatus further comprises a jig attached to the cartridge table and having a coupling member through which the cartridge table is coupled to the carrier device.

With the above arrangement, the cartridge table 316 is coupled to the carrier device 501 by the coupling member. If the carrier device 501 holds the cartridge table 316 and carries the cartridge table 316 upwardly, then the portion of the cartridge table 316 which is held by the carrier device 501 serves as the coupling member. If the carrier device 501 grips and carries the cartridge table 316 upwardly, then the portion of the cartridge table 316 which is gripped serves as the coupling member. The cartridge table 16 may be directly coupled to the carrier device 501 or may be indirectly coupled to the carrier device 501 through the coupling member 337.

According to a preferred aspect of the present invention, the polishing apparatus has a space to allow the carrier device to access the main table.

With the above arrangement, as shown in, for example, FIG. 27, since the base 471 with the space 472 is provided in the polishing apparatus 402, the carrier device 501 which carries the cartridge table 316 can access the main table 454. Then, the cartridge table 316 can be carried onto the support surface 454A of the main table 454 and installed thereon, or the cartridge table 316 can be carried upwardly from the support surface 454A of the main table 454 and detached from the main table 454.

As shown in FIGS. 29A through 29C, since the carrier device 701 is provided, the cartridge table 716 can be carried and installed on the support surface 705A of the main table by the carrier device 701, and can be carried upwardly from the support surface 705A of the main table and detached from the main table 706 by the carrier device 701.

According to a preferred aspect of the present invention, a polishing apparatus further comprises a fastening member for securing the cartridge table to the main table.

With the above arrangement, as shown in, for example, FIGS. 15A and 15B, because the fastening member 318 is provided, the cartridge table 316 can be secured to the main table 305. When the main table 305 is rotated, the polishing tool 315 is rotated in synchronism with the main table 305 for thereby polishing the workpiece 304.

In order to achieve the third object, according to a seventh aspect of the present invention, there is provided a method of assembling a cartridge table, comprising: preparing a cartridge table having a surface on which a polishing tool is mounted, the polishing tool having a polishing surface for polishing a surface of a workpiece; attaching a jig having a coupling member to the cartridge table; coupling the jig attached to the cartridge table through the coupling member to a carrier device; carrying the cartridge table to a position above a support surface of a main table for supporting the cartridge table by the carrier device, and lowering the cartridge table to place the cartridge table onto the support surface by the carrier device; removing the jig from the cartridge table; moving the cartridge table along the support surface of the main table by a moving mechanism which is mounted on a reverse surface of the cartridge table or the support surface of the main table; and positioning the cartridge table with respect to the main table by a positioning member.

According to a preferred aspect of the present invention, the moving mechanism comprises a rolling element which rolls on the support surface of the main table or the reverse surface of the cartridge table.

According to a preferred aspect of the present invention, the positioning member comprises a recess, and the positioning is performed by accommodating the rolling element into the recess.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are views schematically showing an example of deformation such that a polishing surface of a polishing tool loses its planarity, FIG. 1A showing the polishing tool which is not deformed and FIG. 1B showing the polishing tool which is deformed;

FIGS. 2A and 2B are schematic views showing a structure of a polishing tool and a base mounted on a polishing table for use in a polishing apparatus according to a first embodiment of the present invention, FIG. 2A being a cross-sectional view and FIG. 2B being a perspective view;

FIGS. 3A and 3B are schematic views showing a structure of a polishing tool and a base mounted on a polishing table according to a second embodiment of the present invention, FIG. 3A being a cross-sectional view and FIG. 3B being a perspective view;

FIGS. 4A and 4B are schematic views showing a structure of a polishing tool and a base mounted on a polishing table according to a third embodiment of the present invention, FIG. 4A being a cross-sectional view and FIG. 4B being a perspective view;

FIG. 5A and 5B are schematic views showing a structure of a polishing tool and a base mounted on a polishing table according to a fourth embodiment of the present invention, FIG. 5A being a cross-sectional view and FIG. 5B being a perspective view;

FIG. 6 is a schematic cross-sectional view showing a polishing apparatus incorporating the polishing tool having the structure shown in FIGS. 2A-and 2B;

FIG. 7 is a perspective view showing a method of manufacturing a polishing tool assembly according to a fifth embodiment of the present invention;

FIG. 8 is a perspective view showing a method of positioning polishing tool segments and mounting the polishing tool segments on a base;

FIGS. 9A and 9B are plan views showing another method of positioning the polishing tool segments and mounting the polishing tool segments on the base;

FIG. 10A is a vertical cross-sectional view showing the polishing tool assembly which is fixed to a polishing table;

FIG. 10B is a perspective view of the polishing tool assembly shown in FIG. 10A;

FIG. 11 is a perspective view showing a polishing tool assembly according to a sixth embodiment of the present invention;

FIG. 12 is a perspective view showing a polishing tool assembly according to a seventh embodiment of the present invention;

FIG. 13 is a perspective view showing the polishing tool assembly shown in FIG. 12 which is fixed to a polishing table;

FIG. 14 is a cross-sectional side view schematically showing a polishing apparatus which incorporates the polishing tool assembly fixedly mounted on the polishing table shown in FIG. 10 (or FIG. 13);

FIG. 15A is a plan view of a polishing apparatus according to an eighth embodiment of the present invention;

FIG. 15B is a cross-sectional view of a polishing apparatus according to the eighth embodiment of the present invention;

FIG. 16A is a perspective view of a main table and a cartridge table of the polishing apparatus according to the eighth embodiment of the present invention;

FIG. 16B is a plan view of a clamp member of the polishing apparatus according to the eighth embodiment of the present invention;

FIG. 16C is a cross-sectional view of a groove formed in the main table of the polishing apparatus according to the eighth embodiment of the present invention;

FIG. 17 is a bottom view showing the layout of bearing members on the reverse surface of the cartridge table according to the eighth embodiment of the present invention;

FIG. 18A is a cross-sectional view of a bearing member according to the eighth embodiment of the present invention;

FIG. 18B is a view taken along line XVIII-XVIII of FIG. 18A;

FIG. 19A is a cross-sectional view of a recess formed in the main table according to the eighth embodiment of the present invention;

FIG. 19B is a plan view showing the layout of recesses formed in the main table according to the eighth embodiment of the present invention;

FIG. 20A is a front elevational view showing the dimensional relation between a bearing which enters the recess while being in contact with a slant surface of the recess, and the recess;

FIG. 20B is a front elevational view of the bearing which enters the recess in a floating state;

FIG. 20C is a front elevational view of the bearing which enters the recess while being in contact with the slant surface of the recess;

FIG. 21 is a cross-sectional view showing a suspension jig as assembled on a flange of the cartridge table;

FIG. 22 is a perspective view of the suspension jig and the flange shown in FIG. 21;

FIG. 23A is a cross-sectional view of a polishing apparatus according to a ninth embodiment of the present invention;

FIG. 23B is a perspective view of a main table of the polishing apparatus shown in FIG. 23A;

FIG. 24A is a cross-sectional view of a polishing apparatus according to a tenth embodiment of the present invention;

FIG. 24B is a perspective view of a main table of the polishing apparatus shown in FIG. 24A;

FIG. 25A is a cross-sectional view showing the cartridge table and the main table of the polishing apparatus according to the tenth embodiment of the present invention;

FIG. 25B is a plan view of the main table of the polishing table according to the tenth embodiment of the present invention;

FIG. 26 is a plan view of a polishing system incorporating the polishing apparatus according to an embodiment of the present invention;

FIG. 27 is a front elevational view of a hand lifter which suspends a cartridge table with a suspension jig and carries the suspended cartridge table;

FIG. 28 is a front elevational view of the hand lifter when it places the cartridge table on a main table;

FIGS. 29A through 29C are front elevational views of a polishing system having a built-in crane device; and

FIG. 30 is a view showing the manner in which the polishing system shown in FIGS. 29A through 29C suspends a suspension jig having an eye bolt.

BEST MODE FOR CARRYING OUT THE INVENTION

A polishing apparatus according to embodiments of the present invention will be described below with reference to the drawings.

FIG. 2A is a schematic cross-sectional view showing a structure of a polishing tool and a base mounted on a polishing table for use in a polishing apparatus according to a first embodiment of the present invention, and FIG. 2B is a schematic perspective view showing the structure shown in FIG. 2A. In FIGS. 2A and 2B, the reference numeral 10 represents a polishing tool, 20 a polishing tool attachment such as a base, and 30 a polishing table such as a turntable.

The polishing tool 10 comprises a polishing pad made of hard polyurethane foam or the like, or a fixed abrasive. In this embodiment, the disk-shaped fixed abrasive is used as the polishing tool 10. The polishing tool 10 is fixed to an upper surface of the base 20 by an adhesive or the like. The base 20 comprises a disk-shaped member and serves to protect the polishing tool 10 comprising the fixed abrasive and also to allow the polishing tool 10 to easily be mounted on the polishing table 30. The base 20 is made of a material, such as metal or engineering plastics, which has a high mechanical strength and a high chemical resistance. The base 20 has a bolt insertion hole 21 which passes therethrough at a central portion of the base 20. A bolt 40 is inserted through the bolt insertion hole 21 and is screwed into the polishing table 30, so that the base 20 is fastened to the polishing table 30.

The base 20 has an outside diameter slightly larger than that of the polishing tool 10, and hence has a flange projecting radially outwardly from an outer circumferential edge of the polishing tool 10. The flange of the base 20 has a plurality of drive pin insertion holes 22 disposed at substantially equal intervals along the circumferential direction of the base 20, and drive pins 41 are inserted into the drive pin insertion holes 22, respectively, and fixed to the polishing table 30. Each of the drive pin insertion holes 22 has an elongate shape such as an elliptical shape extending in the radial direction of the base 20. Specifically, the width of the drive pin insertion hole 22 in the circumferential direction of the base 20 is slightly larger than the diameter of the drive pin 41, and the length of the drive pin insertion hole 22 in the radial direction of the base 20 is several times longer than the diameter of the drive pin 41. In the portions of the drive pin insertion holes 22, the flange of the base 20 is not fixed in the radial direction thereof with respect to the polishing table 30. Therefore, the base 20 and the polishing tool 10 can be deformed in the radial direction of the polishing table 30 due to thermal expansion thereof caused by the frictional heat and the heat of chemical reaction which are produced by the polishing process. As a result, the polishing surface, i.e., upper surface, of the polishing tool 10 can be kept flat.

One or more drive pins 41 are provided on an upper surface 31 of the polishing table 30 at positions corresponding to positions of the drive pin insertion holes 22 formed in the base 20. Rotation of the polishing table 30 is transmitted to the base 20 and the polishing tool 10 by the bolt 40 and the drive pins 41. Since the drive pins 41 serve to transmit the rotation of the polishing table 30, a load applied to the bolt 40 for transmitting the rotation of the polishing table 30 is reduced.

In the case where the polishing tool 10 has a diameter of up to about 600 mm, the base 20 may be made of a material having a high mechanical strength such as aluminum alloy or engineering plastics so as to provide a sufficient mechanical strength and such a light weight that the base 20 can be handled with ease. Generally, the base 20 having a single integral structure may be used for the purpose of polishing an 8-inch semiconductor wafer.

However, in the case of polishing a semiconductor wafer having a diameter of 12 inches or larger, the polishing tool 10 is required to have a diameter of 700 mm or larger. If the base 20 having such a single integral structure is used for polishing the semiconductor wafer having a diameter of 12 inches or larger, then the base 20 is too heavy to be handled with ease.

In such a case, polishing tool segments as shown in FIGS. 3A and 3B may be used. FIG. 3A is a schematic cross-sectional view showing a modified structure of a polishing tool and a base mounted on a polishing table according to a second embodiment of the present invention, and FIG. 3B is a schematic perspective view, partly exploded, showing the modified structure shown in FIG. 3A. As shown in FIGS. 3A and 3B, the polishing tool segment 10-1 has a fan shape and is fixedly mounted on a base segment (attachment segment) 20-1 which has substantially the same shape as the polishing tool segment 10-1. A plurality of the polishing tool segments 10-1 are mounted on the respective base segments 20-1 and assembled on an upper surface 31 of the polishing table 30 into the polishing tool 10 having a circular or cylindrical shape. A plurality of the base segments 20-1 are assembled into the base 20. Since the polishing tool segment 10-1 and the base segment 20-1 are small in size and weight, respectively, the polishing tool segment 10-1 and the base segment 20-1 can easily be handled.

The fan-shaped base segment 20-1 has one or more bolt insertion holes 23 (two bolt insertion holes in the present embodiment) formed in an inner circumferential portion thereof. The base segment 20-1 is fastened by bolts 24 inserted through the bolt insertion holes 23 into a plate 50, which is secured by the bolt 40 to the central portion of the upper surface 31 of the polishing table 30. Since a plurality of the bolts 24 are used to fasten the respective base segments 20-1 to the polishing table 30, the base segments 20-1 are fixed to the polishing table 30 more firmly than in the case where the respective base segments 20-1 are fixed only by the single bolt 40. The base 20 having the single integral structure as shown in FIGS. 2A and 2B may also be fastened to the polishing table 30 by a plurality of bolts.

The fan-shaped base segment 20-1 may be fastened directly to the polishing table 30 by bolts screwed into bolt insertion holes formed in the polishing table 30, without the plate 50. As with the base 20 shown in FIGS. 2A and 2B, each of the base segments 20-1 has one or more drive pin insertion holes 22 (two drive pin insertion holes in the present embodiment) formed in an outer circumferential portion thereof and having an elliptical shape. A drive pin 41 is inserted into the drive pin insertion hole 22 and fixed to the polishing table 30. In the portions of the drive pin insertion holes 22, the flange of the base segment 20-1 is not fixed in the radial direction thereof with respect to the polishing table 30. The drive pin insertion holes 22 allow the base segments 20-1 and the polishing tool segments 10-1 to be deformed due to thermal expansion in the radial direction of the polishing table 30. Therefore, the polishing surface, i.e., upper surface, of the polishing tool 10 can be kept flat.

The adjacent base segments 20-1 are spaced from each other by a gap having a width represented by {(outer circumferential length of the base 20 or the polishing tool 10 (mm))×(coefficient of linear expansion of the base segment 20-1 or the polishing tool segment 10-1 (1/° C.))×(increase in temperature due to polishing (°C))/(the number of the base segments 20-1) }. The gap is designed so as not to cause the wafer to be polished excessively on the peripheral edge of the wafer by corners of the polishing segments. The gaps and the drive pin insertion holes 22 allow the base segments 20-1 and the polishing tool segments 10-1 to be deformed due to thermal expansion not only in the radial direction of the base 20 or the polishing tool 10 but also in the circumferential direction of the base 20 or the polishing tool 10. As a result, more complete flatness of the polishing surface can be obtained. The width of the gap should preferably be larger than the larger one of the calculated value for the base segments 20-1 and the calculated value for the polishing tool segments 10-1.

The polishing tool 10, which is the assembly of the polishing tool segments 10-1, comprises a polishing pad made of hard polyurethane foam, or a fixed abrasive. The fixed abrasive is produced as follows: First, fine abrasive particles and a binder are mixed with fixed abrasive additives for thereby producing a fixed abrasive material powder. The fixed abrasive additives include an abrasive particle dispersant such as a surface-active agent, a process stabilizer such as a buffer, a process accelerator typified by a pH controller such as KOH, and a mirror finish improver such as a polymeric agent. Each of the materials to be mixed may be in the powder state or in the liquid state. If necessary, pure water may be added to the fixed abrasive material powder, thus producing a mixture. The materials in the mixture are dispersed by an agitator, an ultrasonic dispersing unit, or the like.

Next, the mixture is dried and granulated by a drying device typified by a spray dryer, and thus granulated powdery substance which is formed by uniformly mixing the above materials and has an average diameter of about 50 μm is produced.

The material for the abrasive particles as the materials of the fixed abrasive may be in the powder state or in the slurry state. However, it is preferable to use slurry-like abrasive particles as an abrasive particle material. Since the slurry-like abrasive particles contain fine abrasive particles in a stable state, when the slurry-like abrasive particles are used as the abrasive particle material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Furthermore, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the abrasive particle material should preferably be as small as possible. For example, the amount of metals contained in the abrasive particle material should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although such amount of the metals depends on the type of the abrasive particle material and the ratio of compositions contained in the abrasive particle material.

The material for the binder, which is one of the materials of the fixed abrasive, may be in the powder state or in the slurry state. However, it is preferable to use a latex suspension as a binder material. Since the latex suspension contains its components dispersed uniformly therein, when the latex suspension is used as the binder material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Moreover, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the binder material should preferably be as small as possible. For example, the amount of metals contained in the binder material should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although such amount of the metals depends on the type of the binder material and the ratio of compositions contained in the binder material.

Preferably, a synthetic resin, i.e., a synthetic micromolecular compound (polymer), is selected as the binder. The synthetic micromolecular compound (polymer) is produced by polymerization of a number of monomers. A process for producing the synthetic micromolecular compound comprises various polymerization processes including addition polymerization, copolymerization, condensation polymerization, addition condensation, and the like. The above polymerization processes use water and various chemicals including a polymerization catalyst such as an organometallic compound and an inorganometallic compound, a polymerization inhibitor, a dispersant, an activator, a solvent, a catalyst deactivator, a stabilizer, an emulsifier, an antioxidant, and the like. In this manner, the binder is produced through complex processes. In order to reduce a metallic element mixed in the binder for use in the fixed abrasive, it is preferable to reduce the amount of any metal compounds contained in chemicals and water used in the above various polymerization processes. For example, the amount of metal compounds should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although allowable amount of the metal compounds depends on the polymerization processes, the type of chemicals, and the amount of chemicals remaining in the binder as the product. Pure water or ultrapure water should preferably be used as the above water.

Furthermore, the amount of any metals contained in the fixed abrasive additives as part of the materials of the fixed abrasive should also preferably be as small as possible. The fixed abrasive additives include a process accelerator (amine or the like) including a microcapsule chemical, a process stabilizer (buffer), a mirror finish improver (water-soluble polymer), a polishing auxiliary such as an abrasive particles aggregation inhibitor (organic polymer), an abrasive particle self-generation regulator (resolvent for binder), a fixed abrasive formation auxiliary, and the like. For example, the amount of metals contained in such additives should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although allowable amount the metals depends on the type of the additives, the ratio of addition, or the like. Pure water or ultrapure water should preferably be used.

FIG. 4A is a schematic cross-sectional view showing a structure of a polishing tool and a base mounted on a polishing table according to a third embodiment of the present invention, and FIG. 4B is a schematic perspective view, partly exploded, showing the structure shown in FIG. 4A. In FIGS. 2A and 2B, the drive,pins 41 are positioned in the outer circumferential portion of the base 20 radially outwardly apart from the outer circumferential edge of the polishing tool 10. In FIGS. 3A and 3B, the drive pins 41 are positioned in the outer circumferential portions of the base segments 20-1 radially outwardly apart from the outer circumferential edges of the polishing tool segments 10-1. However, as shown in FIGS. 4A and 4B, the outer circumferential portion of the base segment 20-1 (the base 20) may be secured in position by clamp members 60. In the structure shown in FIGS. 4A and 4B, drive pins 41 and drive pin insertion holes 22 are positioned near the central portion of the polishing table 30. This arrangement allows the base segments 20-1 (the base 20) and the polishing tool segments 10-1 (the polishing tool 10) to be deformed radially inwardly due to thermal expansion. Each of the clamp members 60 has an inverted L-shaped cross section and has two bolt insertion holes 61 formed therein. Bolts 25 are inserted into the respective bolt insertion holes 61 and the tip ends of the respective bolts 25 are screwed into internally threaded holes 32 formed in an outer circumferential portion of the upper surface 31 of the polishing table 30. In this manner, the respective base segments 20-1 (the base 20) are fastened by respective holding portions 62 of the clamp members 60.

In FIGS. 4A and 4B, the segment-type structure comprising the fan-shaped polishing tool segments 10-1 and the fan-shaped base segments 20-1 is shown. As with the structure shown in FIGS. 3A and 3B, a gap having a certain width may be formed between the adjacent polishing tool segments 10-1 and also between the adjacent base segments 20-1 so as to allow the polishing tool segments 10-1 and the base segments 20-1 to be deformed in the circumferential direction.

FIG. 5A is a schematic cross-sectional view showing a structure of a polishing tool and a base mounted on a polishing table according to a fourth embodiment of the present invention, and FIG. 5B is a schematic perspective view, partly exploded, showing the structure shown in FIG. 5A. In FIGS. 2A and 2B, the outer circumferential portion of the base 20 is not fixed to the polishing table 30. In FIGS. 3A and 3B, the outer circumferential portions of the base segments 20-1 are not fixed to the polishing table 30. In FIG. 4A and 4B, the central portion of the base 20 is not fixed to the polishing table 30. However, in the embodiment shown in FIGS. 5A and 5B, the entire lower surface of the base 20 is not fixed to the polishing table 30, and the rotation of the polishing table 30 is transmitted to the base 20 only by the drive pins 41. Specifically, the annular polishing tool 10 having a central hole is fixed to an upper surface of the annular base 20 having a central hole by an adhesive or the like. The base 20 has an outside diameter slightly larger than that of the polishing tool 10, and hence has a flange projecting radially outwardly from an outer circumferential edge of the polishing tool 10. The flange of the base 20 has a plurality of drive pin insertion holes 22 disposed at substantially equal intervals along the circumferential direction of the base 20, and drive pins 41 are inserted into the drive pin insertion holes 22, respectively, and fixed to the polishing table 30. Each of the drive pin insertion holes 22 has an elliptical shape extending in the radial direction of the base 20. In the portions of the drive pin insertion holes 22, the flange of the base 20 is not fixed in the radial direction thereof with respect to the polishing table 30. Therefore, the base 20 and the polishing tool 10 can be deformed without any restraint in the radial direction of the polishing table 30 due to thermal expansion thereof caused by the frictional heat and the heat of chemical reaction which are produced by the polishing process. As a result, the polishing surface, i.e., upper surface, of the polishing tool 10 can be kept flat. In FIGS. 5A and 5B, the reference numeral 43 represents a central pin provided at the central portion of the polishing table 30. The central pin 43 is provided for centering the base 20 having the polishing tool 10 on the polishing table 30 with ease when the base 20 is attached to the polishing table 30.

FIG. 6 is a schematic cross-sectional view showing a polishing apparatus incorporating the polishing tool having the structure shown in FIGS. 2A and 2B. As shown in FIG. 6, the polishing apparatus 100 comprises a top ring 70 provided above the polishing tool 10 for holding a workpiece W to be polished such as a semiconductor substrate on a lower surface thereof, and a dressing member 80 for holding a dressing tool 81 on a lower surface thereof. The polishing apparatus 100 also comprises the polishing tool 10 and the base 20 which are fixed to the polishing table 30. The polishing table 30 is rotatable about its own axis as indicated by the arrow A in FIG. 6. The top ring 70 and the dressing member 80 are vertically movable as indicated by the arrows B and C in FIG. 6, respectively, and are rotatable about their respective axes as indicated by the arrows D and E in FIG. 6, respectively.

The workpiece W held by the top ring 70 is pressed against the polishing surface on the polishing tool 10, and the polishing table 30 and the top ring 70 are rotated relatively to each other, thereby bring the lower surface of the workpiece W into sliding contact with the polishing surface on the polishing tool 10. At the same time, ultrapure water and a chemical liquid are supplied from a polishing liquid supply nozzle 90 onto the polishing surface of the polishing tool 10 for thereby polishing the workpiece W.

After or while the workpiece W is polished, the dressing tool 81 is pressed against the polishing surface on the polishing tool 10 under a predetermined pressure while the dressing member 80 and the polishing table 30 are being rotated. At this time, water is supplied from the polishing liquid supply nozzle 90 onto the polishing surface of the polishing tool 10 for thereby dressing the polishing surface on the polishing tool 10. In this manner, the workpiece W such as a semiconductor wafer is polished by the polishing apparatus 100. The polishing apparatus 100 shown in FIG. 6 has been described by way of example only, and the present invention is not limited to the illustrated polishing apparatus 100. The present invention is also applicable to a polishing apparatus having various other structures.

The embodiments described above are merely preferred embodiments, and various other embodiments can be made without departing from the scope of the present invention. Specifically, various changes and modifications can be made therein within the scope of the inventions described in the claims and also within the scope of technical ideas described in the specification and the drawings. For example, although the polishing table which is rotatable about its own axis is illustrated as a polishing table in the above embodiments, the polishing table is not limited to the illustrated polishing table. For example, the polishing table may perform a reciprocating motion or an eccentric motion. Specifically, the structure of the polishing table is not limited insofar as the workpiece can be polished by a relative motion between the workpiece and the polishing tool mounted on the polishing table.

As described above, according to one aspect of the present invention, since at least a portion of the base is not fixed to the table, even when the base and/or the polishing tool is deformed due to thermal expansion, the deformation is allowed to occur by a portion of the base which is not fixed to the table. Therefore, the polishing surface of the polishing tool can be kept flat.

According to the present invention, since the polishing apparatus has a fixture for fixing the base to the table, the base with the polishing tool fixed thereto can easily be mounted on and dismounted from the table.

According to the present invention, a transmitting member is provided for transmitting movement of the table to the base. With this arrangement, the base and the polishing tool is allowed to be deformed due to thermal expansion at the portion of the base which is not fastened to the table, and the motion of the table can be transmitted to the base.

According to the present, since the base is divided into a plurality of segments, in the case where the polishing tool and the base are large in size, the base with the polishing tool fixedly mounted thereon can easily be handled when the base together with the polishing tool is mounted on and dismounted from the table.

According to the present invention, the above advantages can more efficiently be obtained in the case where the polishing tool comprises the fixed abrasive.

According to the present invention, since the base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times the coefficient of linear expansion of the polishing tool, the polishing tool and the base are deformed substantially equally to each other when thermal expansion occurs due to an increase in temperature caused by the polishing process. Therefore, shearing force acting on the adhesive layer between the polishing tool and the base can be reduced, thus preventing the polishing tool from being detached from the base.

According to the polishing process using the fixed abrasive, generally, the workpiece is polished under a constant pressure to achieve a uniform polishing rate. As described in the second and third embodiments, a polishing tool may have a fixed abrasive divided into a plurality of segments fixedly mounted on a base with predetermined gaps being formed between the segments in a circumferential direction.

With such a polishing tool, large steps are formed on the polishing surface of the fixed abrasive by the gaps. Therefore, when the semiconductor wafer pressed against the polishing surface of the fixed abrasive is brought into sliding contact with the polishing surface over the steps, the contacting areas of the semiconductor wafer with the polishing surface change. In this case, a surface pressure applied to the semiconductor wafer is greatly changed, so that a strong pressure is locally produced. Accordingly, an edge first phenomenon in which a portion of the peripheral edge of the semiconductor wafer is excessively polished may occur to make it difficult to control the polished film at a uniform film thickness within the surface of the semiconductor wafer.

FIG. 7 is a perspective view showing a method of manufacturing a polishing tool assembly 101 according to a fifth embodiment of the present invention. The polishing tool assembly according to the fifth embodiment can eliminate an edge first phenomenon described above and uniformly process the workpiece.

As shown in FIG. 7, the polishing tool assembly 101 comprises a plurality of polishing tool segments 110-1 through 110-6 (six segments in the present embodiment) which constitute a polishing tool 110 of a fixed abrasive as a whole. The polishing tool 110 has a polishing surface thereon for polishing a workpiece to be polished, such as a semiconductor wafer. The polishing tool segments 110-1 through 110-6 are fixedly mounted and held on a single polishing tool attachment (base) 120 in such a state that side edges 111 of the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with each other. The components of the polishing tool assembly 101 will be described in detail below.

The polishing tool segments 110-1 through 110-6 have the same shape in a fan-shaped form and the same dimension. The side edges 111 of the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with and fixed to each other, for thereby forming the cylindrical polishing tool 110 as a whole. Specifically, the polishing tool segments 110-1 through 110-6 are divided radially at equal angles around the center of the polishing tool 110 so as to have the same shape and dimension. In the present embodiment, the polishing tool segments 110-1 through 110-6 are in a fan-shaped form having the same central angle.

Each of the polishing tool segments 110-1 through 110-6 is produced as follows: First, fine abrasive particles and a binder are mixed with fixed abrasive additives (as needed) for thereby producing a fixed abrasive material powder. The fixed abrasive additives include an abrasive particle dispersant such as a surface-active agent, a process stabilizer such as a buffer, a process accelerator typified by a pH controller such as KOH, and a mirror finish improver such as a polymeric agent. Each of the materials to be mixed may be in the powder state or in the liquid state. If necessary, pure water may be added to the fixed abrasive material powder, thus producing a mixture. The materials in the mixture are sufficiently dispersed by an agitator, an ultrasonic dispersing unit, or the like.

Next, the mixture is dried and granulated by a drying device typified by a spray dryer, and thus granulated powdery substance which is formed by uniformly mixing the above materials and has an average diameter of about 50 μm is produced. Alternatively, particles may be formed in the liquid and then filtered to produce a powder to be formed.

The material for the abrasive particles as the materials of the fixed abrasive may be in the powder state or in the slurry state. However, it is preferable to use slurry-like abrasive particles as an abrasive particle material. Since the slurry-like abrasive particles contain fine abrasive particles in a stable state, when the slurry-like abrasive particles are used as the abrasive particle material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Furthermore, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the abrasive particle material should preferably be as small as possible.

The material for the binder, which is one of the materials of the fixed abrasive, may be in the powder state or in the slurry state. However, it is preferable to use a latex suspension as a binder material. Since the latex suspension contains its components dispersed uniformly therein, when the latex suspension is used as the binder material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Moreover, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the binder material should preferably be as small as possible.

Preferably, a synthetic resin, i.e., a synthetic micromolecular compound (polymer), is selected as the binder. The synthetic micromolecular compound (polymer) is produced by polymerization of a number of monomers. A process for producing the synthetic micromolecular compound comprises various polymerization processes including addition polymerization, copolymerization, condensation polymerization, addition condensation, and the like. The above polymerization processes use water and various chemicals including a polymerization catalyst such as an organometallic compound and an inorganometallic compound, a polymerization inhibitor, a dispersant, an activator, a solvent, a catalyst deactivator, a stabilizer, an emulsifier, an antioxidant, and the like. In this manner, the binder is produced through complex processes. In order to reduce a metallic element mixed in the binder for use in the fixed abrasive, it is preferable to reduce the amount of any metal compounds contained in chemicals and water used in the above various polymerization processes.

Furthermore, the amount of any metals contained in the fixed abrasive additives as part of the materials of the fixed abrasive should also preferably be as small as possible. The fixed abrasive additives include a process accelerator (amine or the like) including a microcapsule chemical, a process stabilizer (buffer), a mirror finish improver (water-soluble polymer), a polishing auxiliary such as an abrasive particles aggregation inhibitor (organic polymer), an abrasive particle self-generation regulator (resolvent for binder), a fixed abrasive formation auxiliary, and the like.

The granulated powdery substance produced by the above process are formed into the polishing tool segments 110-1 through 110-6, which constitute the polishing tool 110, by a compression molding process, typically, a hot pressing process. The size of a compression molding machine used in the compression molding process is determined by the size of a polishing tool to be produced. Therefore, the divided polishing tool segments 110-1 through 110-6 can be produced with a smaller compression molding machine in comparison with a compression molding machine producing an unseparated polishing tool, i.e., a disk-shaped or cylindrical polishing tool. Accordingly, incidental equipments and equipments in subsequent processes can be made smaller in size, and hence initial investments and manufacturing cost of the polishing tool can be reduced.

As described above, the side edges 111 of the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with each other to form the cylindrical polishing tool 110. In this state, the polishing tool 110 composed of the polishing tool segments 110-1 through 110-6 is fixedly mounted on the base 120 by an adhesive or the like in such a manner that certain pressures are uniformly applied to the respective polishing tool segments 110-1 through 110-6, for thereby producing the polishing tool assembly 101. The polishing tool segments 110-1 through 110-6 mounted on the base 120 become a cylindrical shape as a whole. The side edges 111 of the polishing tool segments 110-1 through 110-6 are held in close contact with each other so that gaps are not intentionally formed between the polishing tool segments 110-1 through 110-6. If the side edges 111 do not have perfectly flat surfaces, the entire surfaces of the side edges 111 cannot be held in contact with each other. The entire surfaces of the side edges 111 of the adjacent polishing tool segments 110-1 through 110-6 may not be held in contact with each other as long as at least a portion of the side edge 111 of the polishing tool is held in contact with at least a portion of the side edge 111 of the adjacent polishing tool.

The base 120 has a single integral cylindrical shape and serves to protect the polishing tool segments 110-1 through 110-6 of the polishing tool 110 and also to facilitate the attachment of the polishing tool 110 to a CMP apparatus. The base 120 is made of a material having a high mechanical strength, such as metal or engineering plastics. The base 120 has a hole 121 formed in the central portion thereof for inserting a bolt therethrough. The base 120 has an outside diameter slightly larger than the polishing tool 110 (the polishing tool segments 110-1 through 110-6), and thus a radially outwardly projecting portion 123 is provided at a peripheral edge of the base 120. The radially outwardly projecting portion 123 serves as an attachment portion for attaching the base 120 to a polishing table 150, which will be described later.

In the case where the polishing tool 110 comprises many polishing tool segments or the polishing tool segments have complicated shapes, it is difficult to position the polishing tool segments 110-1 through 110-6 with respect to each other. If the polishing tool segments 110-1 through 110-6 are inaccurately positioned with respect to each other, then, in mounting the polishing tool segments 110-1 through 110-6 on the base 120, the adhesive applied to bond the polishing tool segments 110-1 through 110-6 to the base 120 may ooze out from the gaps between the opposed side edges 111 of the adjacent polishing tool segments 110-1 through 110-6 and thus leak onto the polishing surface of the polishing tool 110. The adhesive on the polishing surface prevents the polishing of a semiconductor wafer or causes a scratch on a surface of a semiconductor wafer. According to the present invention, the adhesive is not applied to the side edges 111 of the polishing tool segments 110-1 through 110-6, but is applied only to the contacting surfaces of the polishing tool segments 110-1 through 110-6 and the base 120.

Further, gaps formed between the polishing tool segments 110-1 through 110-6 would change contacting areas of the semiconductor wafer with the polishing surface on the polishing tool 110. Because it is difficult to instantaneously change a pressure applied to the semiconductor wafer during the polishing process, the change of the contacting areas of the semiconductor wafer with the polishing surface on the polishing tool 110 changes a surface pressure (polishing pressure) applied to the semiconductor wafer, thus causing change of the processing rate (polishing rate) of the semiconductor wafer. Particularly, since large forces are applied to the semiconductor wafer when the peripheral edge of the semiconductor wafer crosses the gaps between the polishing tool segments 110-1 through 110-6, the peripheral edge portion of the semiconductor wafer is excessively polished.

According to the present embodiment, since the polishing tool segments 110-1 through 110-6 are in a fan-shaped form, the polishing tool segments 110-1 through 110-6 are assembled radially inwardly on the base 120 and fixed thereon so as to form outer circumferential edges of the polishing tool segments 110-1 through 110-6 into a circular shape. Therefore, the polishing tool segments 110-1 through 110-6 can easily be positioned with respect to each other. For example, as shown in FIG. 8, an annular positioning ring 130 is mounted as a positioning member around the polishing tool segments 110-1 through 110-6 assembled on the base 120, for thereby positioning the polishing tool segments 110-1 through 110-6 with respect to each other. After the polishing tool segments 110-1 through 110-6 positioned with the positioning ring 130 are bonded to the base 120, the positioning ring 130 is removed from the polishing tool segments 110-1 through 110-6. In this manner, the polishing tool segments 110-1 through 110-6 can be brought into close contact with each other so as to minimize gaps between the adjacent polishing tool segments 110-1 through 110-6. Therefore, the adhesive applied to bond the polishing tool segments 110-1 through 110-6 and the base 120 is prevented from oozing out from the gaps and leaking onto the polishing surface of the polishing tool 110. Since the polishing tool thus constructed has substantially no gaps between the polishing tool segments 110-1 through 110-6, the semiconductor wafer can be prevented from being excessively polished near the edge portion thereof in the polishing process and can uniformly be polished over the entire surface thereof.

The polishing tool segments 110-1 through 110-6 assembled on the base 120 may be positioned by various positioning members other than the annular positioning ring 130. Any positioning member may be used as long as it can support the fan-shaped (or sectorial) polishing tool segments 110-1 through 110-6 so as to form the outer circumferential edges of the polishing tool segments 110-1 through 110-6 into a circular shape. For example, a clamp mechanism shown in FIG. 9A may be used as a positioning member. As shown in FIG. 9A, the clamp mechanism 140 comprises two arcuate arms 141, 143 which can form a ring as a whole, a pivot shaft 145 such as a hinge for pivotally coupling ends of the arms 141, 143, and fastening mechanisms 147, 149 mounted on the other ends of the arms 141, 143. As shown in FIG. 9B, outer circumferential edges of the assembled polishing tool segments 110-1 through 110-6 are clamped by the arcuate arms 141, 143. The arcuate arms 141, 143 are fastened to each other with the fastening mechanisms 147, 149 for thereby positioning the polishing tool segments 110-1 through 110-6 with respect to each other. After the polishing tool segments 110-1 through 110-6 positioned with the clamp mechanism 140 are bonded to the base 120, the clamp mechanism 140 is removed from the polishing tool segments 110-1 through 110-6, for thereby producing the polishing tool assembly 101.

When the polishing tool 110 comprises a plurality of polishing tool segments 110-1 through 110-6, it is not necessary to handle a large piece of polishing tool, which tends to crack in the manufacturing process, and air bubbles are less introduced into the adhesive layer applied to bond the polishing tool segments 110-1 through 110-6 to the base 120 than in the case where a single integral piece of polishing tool is employed. The air bubbles introduced into the adhesive layer tend to produce unbonded areas below the polishing surface of the polishing tool. Such air bubbles prevent the polishing tool from being firmly fixed to the base 120, and are liable to allow the polishing tool to be broken under frictional forces produced when the polishing tool is brought into sliding contact with the semiconductor wafer.

FIGS. 10A and 10B show the polishing tool assembly 101 manufactured as described above which is fixed to the polishing table 150. FIG. 10A is a vertical cross-sectional view of the polishing tool assembly 101, and FIG. 10B is a perspective view of the polishing tool assembly 101. As shown in FIGS. 10A and 10B, the polishing table 150 is in the form of a disk and has an upper surface serving as a base fixing surface 151 which has a larger area than the lower surface of the base 120. The polishing table 150 has a fixing portion 153 in the form of an internally threaded hole formed at the central portion thereof, and fixing portions 155 in the form of internally threaded holes formed in a plurality of locations (three locations in the present embodiment) at a peripheral portion thereof. A bolt is screwed into the fixing portion 153 and two bolts are screwed into each of the fixing portion 155.

The polishing tool assembly 101 is fastened to the polishing table 150 as follows: The polishing tool assembly 101 is placed on the polishing table 150, and a bolt 170 is inserted through a central hole 113 in the polishing tool 110 and the bolt insertion hole 121 in the base 120 and screwed into the fixing portion 153 in the polishing table 150. Three clamp members 175 having an inverted L-shaped cross section are placed respectively on the attachment portion 123 at the peripheral edge of the base 120. Bolts 179 are inserted through two bolt insertion holes 177 formed in each of the clamp members 175 and screwed into the fixing portions 155 in the polishing table 150. Thus, the clamp members 175 press the base 120 downwardly against the polishing table 150 with upper holding portions 176 thereof.

The bolt insertion hole 121 in the base 120 has an inside diameter smaller than the hole 113 in the polishing tool 110 so as to provide a step between the upper surface of the polishing tool 110 and the upper surface of the base 120. The step is used to accommodate the head of the bolt 170 which fastens the base 120 to the polishing table 150.

Since the polishing tool assembly 101 is fastened at the central portion and the circumferential portions, the polishing tool assembly 101 is easily and reliably positioned on the polishing table 150 for axial alignment, and is firmly secured to the polishing table 150.

FIG. 11 is a perspective view showing a polishing tool assembly according to a sixth embodiment of the present invention. In the above embodiment, each of the polishing tool segments 110-1 through 110-6 is in a fan-shaped form. However, as shown in FIG. 11, a polishing tool assembly 101-2 may comprise sectorial polishing tool segments 110-1 through 110-6 which have the same shape and dimension. Side edges 111 of the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with and fixed to each other, for thereby forming the disk-shaped polishing tool 110. In the embodiment shown in FIG. 11, it is not necessary to form the bolt insertion hole 121 in the central portion of the base 120, which is shown in FIG. 7. The polishing tool segments 110-1 through 110-6 may be divided radially at equal angles around the center of the polishing tool 110 so as to have the same shape and dimension. For example, the polishing tool segments 110-1 through 110-6 may be in a quadrantal form. For attaching the polishing tool assembly 101-2 to the polishing table 150 as shown in FIGS. 10A and 10B, the polishing tool assembly 101-2 is fastened to the polishing table 150 only by the clamp members 175 placed on the peripheral edge of the base 120. The polishing tool assembly 101-2 may be fastened to the polishing table 150 by various mechanisms other than the clamp members 175. The polishing tool assembly 101 shown in FIG. 7 may also be fixed to the base 120 by various mechanisms other than the clamp members 175.

When the polishing tool 110 has a diameter of up to about 600 mm, the base 120 may be made of a material such as aluminum alloy or engineering plastics so as to provide a sufficient mechanical strength and such a light weight that the base 120 can be handled with ease. Generally, a rotatable thick polishing tool for polishing an 8-inch semiconductor wafer can be manufactured by the above process.

FIG. 12 is a perspective view showing a polishing tool assembly according to a seventh embodiment of the present invention. For polishing a semiconductor wafer having a diameter of 12 inches or larger, however, a polishing tool needs to have a diameter of 700 mm or larger. If the base 120 having a single integral structure is used for polishing the semiconductor wafer having a diameter of 12 inches or larger, then the base 120 is too heavy to be handled with ease. In such a case, a polishing tool assembly 101-3 as shown in FIG. 12 may be used. The polishing tool assembly 101-3 has a plurality of base segments (attachment segments) 120-1 through 120-6 (six segments in the present modification) divided so as to correspond to the polishing tool segments 110-1 through 110-6. The polishing tool segments 110-1 through 110-6 are fixed respectively to the independent base segments 120-1 through 120-6 by an adhesive or the like. As shown in FIG. 13, the base segments 120-1 through 120-6 on which the polishing tool segments 110-1 through 110-6 are mounted are placed on the polishing table 150 so that the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with each other. The base segments 120-1 through 120-6 have respective attachment portions 123-1 through 123-6, which are fastened to the polishing table 150 by respective six clamp members 175 in the same manner as FIGS. 10A and 10B. Further, the bolt 170 is inserted through the central hole 113 to fasten the polishing tool assembly 101-3 to the polishing table 150. In this modification, the components of the polishing tool assembly 101-3 can be handled with ease. In the case where the polishing tool segments 110-1 through 110-6 have sectorial shapes, the base segments 120-1 through 120-6 may also have sectorial shapes.

When a material preparing step including mixing and dispersing materials, a granulating step, a forming step, and steps of mounting and bonding components are performed in an environment into which clean air is supplied through a filter installed in a clean room, a clean booth, or the like, it is possible to manufacture a highly clean polishing tool (fixed abrasive).

With the polishing tool assembly manufactured by the above process, a semiconductor wafer can be processed with high quality. Further, this polishing tool assembly can easily and inexpensively be manufactured and can be handled with ease.

FIG. 14 is a cross-sectional side view schematically showing a polishing apparatus 200 which incorporates the polishing tool assembly 101 fixedly mounted on the polishing table 150 shown in FIG. 10B (or FIG. 13). As shown in FIG. 14, the polishing apparatus 200 comprises a top ring (workpiece holding device) 210 for holding a semiconductor wafer (workpiece) W to be polished on a lower surface thereof, a dressing member 220 for holding a dressing tool 221 on a lower surface thereof, and the polishing table 150 on which the polishing tool assembly 101 is fixedly mounted. The polishing table 150 is rotatable about its own axis as indicated by the arrow. The top ring 210 and the dressing member 220 are vertically movable as indicated by the arrows, respectively, and rotatable about their respective axes as indicated by the arrows, respectively.

The semiconductor wafer W held by the top ring 210 is pressed against the upper polishing surface on the polishing tool assembly 101, and the polishing tool assembly 101 and the top ring 210 are rotated independently of each other to bring the lower surface of the semiconductor wafer W into sliding contact with the upper polishing surface on the polishing tool 110. At the same time, a polishing liquid (abrasive liquid) is supplied onto the upper polishing surface of the polishing tool assembly 101 from a polishing liquid supply nozzle 230 to thus polish the semiconductor wafer W.

After or while the semiconductor wafer W is polished, the dressing process is preformed as follows. While the dressing member 220 and the polishing tool assembly 101 are being rotated, the dressing tool 221 is pressed against the polishing surface on the polishing tool 110 under a predetermined pressure. At the same time, water is supplied from a water supply nozzle 223 onto the polishing surface, for thereby dressing the polishing surface on the polishing tool 110. In this manner, the semiconductor wafer W is polished with the polishing apparatus 200 incorporating the polishing tool assembly 101 according to the present invention. The polishing apparatus according to the present invention is not limited to the polishing apparatus 200 shown in FIG. 14. The present invention is also applicable to a polishing apparatus having other structures.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various other embodiments may be made without departing from the scope of the present invention. Specifically, it should be understood that various changes and modifications may be made within the scope of the inventions described in the appended claims and also within the scope of technical concepts described in the specification and the drawings. Any shapes, structures, and materials which are not described directly in the specification and the drawings may fall within the scope of technical concepts of the present invention as long as they provide operations and advantages according to the present invention.

As described in detail above, the present invention provides the following advantages:

(1) According to the present invention, the circumferentially adjacent polishing tool segments are held in close contact with each other. Therefore, when the workpiece is brought into sliding contact with the polishing surface across the polishing tool segments, a pressure acting on the surface of the workpiece does not change, and hence the surface of the workpiece can uniformly be processed.

(2) Since the polishing tool assembly comprises a plurality of polishing tool segments, each of the polishing tool segments can be made small in size, and the polishing tool assembly can be manufactured with small-scale equipments for forming the polishing tool assembly. Thus, initial investments and the manufacturing cost of the polishing tool assembly can be reduced. Since each of the polishing tool segments is small in size, it can be handled with ease, and the polishing tool assembly can easily be manufactured with high cleanliness and high quality.

(3) Each of the polishing tool segments is in a sectorial or fan-shaped form, and the circumferentially adjacent polishing tool segments are held in close contact with and fixed to each other. Therefore, even though the polishing tool assembly comprises a plurality of polishing tool segments, the polishing tool segments can easily be positioned with respect to each other so as to form a disk or cylindrical shape as a whole when the polishing tool segments are fixedly mounted on the polishing tool attachment. As a result, the polishing tool assembly can be replaced with a small expenditure of labor and time in a simple process.

(4) According to the present invention, the polishing tool attachment on which the polishing tool segments are mounted is divided into a plurality of attachment segments so as to correspond to the polishing tool segments. Therefore, even if the polishing tool assembly has a large diameter and is heavy, the polishing tool segments can easily be handled together with the respective attachment segments. Accordingly, a smaller space is required in a clean room for replacing the polishing tool assembly, and the polishing tool assembly can be handled with ease in the clean room.

An eighth embodiment of the present invention will be described below with reference to FIGS. 15A, 15B and 16A through 16C. Identical or corresponding parts are denoted by identical reference numerals throughout FIGS. 15A, 15B and 16A through 16C, and repetitive description is eliminated.

FIGS. 15A and 15B are views showing a polishing apparatus 401 according to the eighth embodiment of the present invention. FIG. 16A is a perspective view of a main table 305 of the polishing apparatus 401, FIG. 16B is a plan view of a clamp member 318, and FIG. 16C is a cross-sectional view of a groove 342 formed in the main table 305.

The polishing apparatus 401 comprises a flanged cartridge table 316 to which a fixed abrasive 315 serving as a polishing tool is attached, a main table 305 on which the cartridge table 316 is mounted, a top ring 301 for holding a semiconductor wafer 304 as a workpiece to be polished, rotating the semiconductor wafer 304, and pressing the semiconductor wafer 304 against the main table 305, and a liquid supply nozzle 310 for supplying water or a chemical L to the fixed abrasive 315 during polishing. The fixed abrasive 315 is attached to a surface 316A of the cartridge table 316. The main table 305 is disposed so as to face a reverse surface 316B of the cartridge table 316 opposite to the surface 316A thereof.

The fixed abrasive 315 is in the form of a disk having a diameter of about 60 cm, and bonded to the surface 316A of the cartridge table 316 made of aluminum or the like by an adhesive. The cartridge table 316 has a flange 316C on its outer circumferential edge. When clamp members 318 serving as fastening members are fixed to the main table 305 by bolts, the clamp members 318 press the flange 316C against the main table 305 for thereby securing the cartridge table 316 to a surface 305A of the main table 305. Specifically, the bolts 319 are screwed into internally threaded holes 320 formed in the main table 305, and hence the cartridge table 316 is fixed to the main table 305 by the clamp members 318. At this time, the reverse surface 316B of the cartridge table 316 is held in contact with the surface 305A of the main table 305 which supports the cartridge table 316. Thus, the surface 305A of the main table 305 serves as a support surface for supporting the cartridge table 316.

As shown in FIGS. 16A through 16C, each of the clamp members 318 is of a structure which is relatively wide and has arcuate sides 318A and 318B. The arcs of the arcuate sides 318A and 318B have a common center O, and the clamp member 318 has opposite ends 318C whose extensions intersects at the common center O at an angle of about 45°. When the clamp members 318 press the flange 316C of the cartridge table 316 against the surface 305A of the main table 305 and are fastened to the main table 305 by the bolts 319, the cartridge table 316 is fixed to the main table 305. Therefore, the cartridge table 316 can easily be mounted on and dismounted from the main table 305 by attaching and detaching the clamp members 318. The two bolts 319 are used for each of the clamp members 318. Because the relatively wide clamp members 318 are used to press and secure the flange 316C of the cartridge table 316 to the main table 305, the polishing surface of the fixed abrasive 315 is less likely to be distorted or deformed under pressing forces from the clamp members 318.

The flange 316C of the cartridge table 316 has circumferentially spaced projections 329 projecting radially outwardly therefrom. Each of the projections 329 has an internally threaded hole 330 formed therethrough for the insertion of a pusher bolt 331 (or suspension bolt (not shown)) therein. The internally threaded holes 330 are used to insert the respective pusher bolts 331 therethrough for removing the cartridge table 316 from the main table 305. Specifically, in order to remove the cartridge table 316 from the main table 305, the pusher bolts 331 are inserted into the internally threaded holes 330 and turned until tip ends 331A of the pusher bolts 331 are brought into contact with the bottoms 342A of grooves 342 formed in the main table 305. When the pusher bolts 331 are further turned, the torque of the pusher bolts 331 is converted into forces by which the cartridge table 316 is removed from the main table 305. The grooves 342 are formed in the surface 305A of the main table 305 so as to be positioned directly below the internally threaded holes 330 of the cartridge table 316. The grooves 342 serve to receive the tip ends 331A of the pusher bolts 331 (or suspension bolt) for protecting the surface 305A of the main table 305 so as not to be damaged.

In the present embodiment, the polishing apparatus 401 has four clamp members 318 and four projections 329. However, in view of usage conditions such as the pressing load applied by the clamp members 318, an annular clamp member 318 may be used to press the entire circumference of the cartridge table 316. The number of projections 329 may be increased or decreased in view of the weight of the cartridge table 316 and the adhesion strength between the cartridge table 316 and the main table 305. The cartridge table 316 to which the fixed abrasive 315 is attached may be made of ceramics, stainless steel, titanium, synthetic resin, or the like as well as aluminum for corrosion resistance.

FIG. 17 is a bottom view of the cartridge table 316. As shown in FIG. 17, the cartridge table 316 has six bearing members 322 serving as a moving mechanism incorporated therein. The bearing members 322 are disposed in point symmetry with respect to a center C1 of the reverse surface 316B of the cartridge table 316, and spaced at an equal distance R from the center C1. Adjacent ones of the bearing members 322 are angularly spaced from each other by an angle of 60° with respect to the center C1. The reverse surface 316B of the cartridge table 316 serves as a bearing attachment surface. The cartridge table 316 or the main table 305 may incorporate one bearing member 322, but should preferably incorporate three or more bearing members 322. Since the bearing members 322 are incorporated in the cartridge table 316, a liquid such as a waste slurry or pure water does not flow into the bearing members 322. Thus, it is desirable to incorporate the bearing members 322 in the cartridge table 316 rather than in the surface 305A of the main table 305.

As shown in FIGS. 18A and 18B, each of the bearing members 322 comprises a holder 323, a ball bearing 324 comprising a spherical ball, a spacer 325, a bearing retainer plate 326, and four flat countersunk head screws 327. The ball bearing 324 constitutes a rolling element. The holder 323 comprises a downwardly opened cubic casing having a flat square upper surface 323A having a width slightly wider than the outside diameter of the ball bearing 324, and hence the ball bearing 324 is rotatably housed in the holder 323. The holder 323 may alternatively comprise a downwardly opened cylindrical cup having a flat upper circular surface 323A having a diameter slightly greater than the outside diameter of the ball bearing 324. The ball bearing 324 is pushed through an opening 328 of the holder 323 into the holder 323, and has a portion projecting downwardly from the holder 323 through the opening 328. The bearing retainer plate 326 which has a circular opening 332 formed therein is disposed beneath the ball bearing 324. The ball bearing 324 has a portion projecting downwardly from the bearing retainer plate 326 through the opening 332. The bearing retainer plate 326 prevents the ball bearing 324 from being dislodged from the holder 323. The spacer 325 is disposed between the holder 323 and the bearing retainer plate 326. The ball bearing 324 has a portion projecting downwardly from the reverse surface 316B of the cartridge table 316. FIG. 18B is a view taken along line XVIII-XVIII of FIG. 18A.

As shown in FIGS. 19A and 19B, a plurality of recesses 333 are formed in the surface 305A of the main table 305 so as to serve as positioning members having an inverted conical shape. The recesses 333 are disposed in point symmetry with respect to a center C2 of the surface 305A of the main table 305, and spaced at an equal distance R from the center C2. The recesses 333 are arranged in the same pattern as the ball bearings 324 (the bearing members 322) arranged on the reverse surface 316B of the cartridge table 316 (see FIG. 17). The ball bearings 324 (indicated by the double-dot-dash line in FIG. 19A) sliding or rolling on the surface 305A fall into the respective recesses 333, and have respective portions 324A projecting downwardly from a hypothetical extension 305B of the surface 305A into the respective recesses 333. Each of the ball bearings 324 comprises a spherical ball.

As shown in FIGS. 18A and 18B, each of the bearings 324 rides on a circumferential edge of the recess 333 along the surface 305A, and has its uppermost end which is spaced from the upper surface 323A of the holder 323 by a small gap so that the reverse surface 316B of the cartridge table 316 is held in close contact with the surface 305A of the main table 305. The small gap is selected such that when an attempt is made to move the cartridge table 316 after the ball bearings 324 enter the respective recesses 333, the ball bearings 324 are elevated into contact against the upper surface 323A, but do not move upwardly out of the respective recesses 333. Since the holders 323, the ball bearings 324, and the recesses 333 are thus dimensioned and shaped, the cartridge table 316 can be positioned accurately with respect to the main table 305.

As shown in FIG. 20A, there may be a situation in which each of the ball bearings 324 contacts a slant surface 333A of the recess 333. The relationship in such a situation between the radius r of the ball bearing 324, the radius R of the inlet area of the recess 333, and the depth h of the recess 333 will be described below. In this situation also, the surface 305A of the main table 305 is held in close contact with the reverse surface 316B of the cartridge table 316. It is assumed that the lowest point M (in FIG. 20A) of the recess 333 is spaced from the center C of the ball bearing 324 by a distance m and the uppermost end (in FIG. 20A) of the ball bearing 324 is spaced from the surface 305A (the reverse surface 316B) by a distance Z. The slant surface 333A of the recess 333 has a length (R²+h²)^(1/2). If the foot of the perpendicular to the slant surface 333A of the recess 333 from the center C of the ball bearing 324 is represented by P and the foot of the perpendicular to a line segment CM from a point N of intersection between the surface 305A and the slant surface 333A of the recess 333 is represented by Q, then the triangle PCM and the triangle QNM are right triangles and similar triangles. In this case, CP=r, CM=m, NQ=R, and NM=(R²+h²)^(1/2), and the following expressions are established: m:(R²+h²)^(1/2)=r:R hence, m=r·(R²+h²)^(1/2)/R Z = r + m − h   = r + r ⋅ (R² + h²)^(1/2)/R − h   = r(1 + (1 + (h/R)²)^(1/2)) − h

When the ball bearing 324 actually enters the recess 333, the ball bearing 324 either floats from the recess 333 as shown in FIG. 20B, or rides in the recess 333 in contact with the slant surface 333A of the recess 333 as shown in FIG. 20C.

In the case of FIG. 20B, there are plays between the ball bearing 324 and the recess 333 and also between the ball bearing 324 and the upper surface 323A of the holder 323. At this time, the ball bearing 324 is held in contact with the bearing retainer plate 326, and does not further project downwardly from the holder 323. When the cartridge table 316 slightly moves on the main table 305, the ball bearing 324 also slightly moves into contact with the slant surface 333A of the recess 333. In this case, the ball bearing 324 is pressed against the slant surface 333A and withdrawn upwardly into the holder 323, so that the uppermost end of the ball bearing 324 contacts the upper surface 323A of the holder 323. Since the ball bearing 324 cannot further move upwardly in this state, the ball bearing 324 acts as a stopper, thus preventing the cartridge table 316 from moving further on the main table 305.

If the distance from the surface 305A (the reverse surface 316B) to the upper surface 323A is represented by S and the distance from the surface 305A (the reverse surface 316B) to the uppermost end (in FIG. 20B) of the ball bearing 324 is represented by Z′, then the following expression is satisfied:

-   -   (1) Z′≦S<2r (in the case of FIG. 20B) (The relationship Z′=S is         satisfied when there is no gap (play) between the uppermost end         of the ball bearing 324 and the upper surface 323A of the holder         323.)

In the case of FIG. 20C, the ball bearing 324 contacts the upper surface 323A of the holder 323, but does not contact the bearing retainer plate 326. In this case, since the ball bearing 324 cannot move upwardly in the recess 333, the ball bearing 324 serves as a stopper for preventing the cartridge table 316 from moving on the main table 305.

Since the distance from the surface 305A (the reverse surface 316B) to the upper surface 323A of the holder 323 is represented by S and the distance from the surface 305A (the reverse surface 316B) to the uppermost end (in FIG. 20C) of the ball bearing 324 is represented by Z, the following expression is satisfied:

-   -   (2) Z=S<2r (in the case of FIG. 20C) If there is a gap (play)         formed between the uppermost end of the ball bearing 324 and the         upper surface 323A of the holder 323, then the following         expression is satisfied:     -   (3) Z<S<2R

For example, if the shapes and dimensions of the holder 323 and the recess 333 are determined to satisfy the expressions (1), (2) and (3), then the cartridge table 316 and the main table 305 can be positioned in order to keep the surface 305A and the reverse surface 316B in close contact with each other. When the cartridge table 316 and the main table 305 are thus positioned, the reverse surface 316B is not caused to float off from the surface 305A by the ball bearing 324.

Referring back to FIGS. 19A and 19B, there are six recesses 333 which are disposed in point symmetry with respect to the center C2 of the surface 305A of the main table 305, and spaced at an equal distance R from the center C2. The recesses 333 are angularly spaced at angular intervals of 60° on a circle having the radius R about the center C2. Since the recesses 333 are arranged in the same pattern as the ball bearings 324, the ball bearings 324 that move on the surface 305A can easily enter the respective recesses 333. When the ball bearings 324 enter the respective recesses 333, the cartridge table 316 is positioned on the main table 305. The cartridge table 316 can be positioned in six patterns in which the cartridge table 316 is turned and shifted by an angle of 60° with respect to each other on the main table 305, and can easily be positioned on the main table 305 irrespective of the attitude (or posture) of the cartridge table 316 carried on the main table 305. However, the cartridge table 316 needs to be placed on the main table 305 in a posture parallel to the main table 305. FIG. 19B is a plan view of the structure shown in FIG. 19A.

An arrangement for suspending the cartridge table 316 will be described below.

As shown in FIG. 21, the cartridge table 316 has a detachable suspension jig 335. The suspension jig 335 is attached to the flange 316C of the cartridge table 316 through internally threaded holes 334 formed in the flange 316C of the cartridge table 316. The suspension jig 335 comprises a disk-shaped suspension jig body 336 having a cavity 336A defined in a lower portion thereof, and a flange 337 mounted on an upper portion of the suspension jig body 336 and having a radius smaller than the radius of the suspension jig body 336. The cavity 336A in the suspension jig body 336 is surrounded by an annular wall 340 having internally threaded holes 338 formed therein. The internally threaded holes 338 extend axially through the annular wall 340. The flange 337 serving as a coupling member is joined to the suspension jig body 336 by a shaft 341.

The suspension jig 335 is fastened to the flange 316C of the cartridge table 316 by hexagon socket head cap bolts 339 which are screwed into the internally threaded holes 338 and 334. Instead of the hexagon socket head cap bolts 339, the pusher bolts 331 (see FIG. 16A) may be screwed into the internally threaded holes 334, and may be used to suspend the cartridge table 316. In the case where the suspension jig 335 is mounted on the flange 316C and the flange 337 is supported to suspend the cartridge table 316, then because the surface 316A of the cartridge table 316 and the fixed abrasive 315 are housed in the cavity 336A, the surface 316A of the cartridge table 316 and the fixed abrasive 315 do not hit other devices while being suspended, and hence are prevented from being broken or damaged. FIG. 22 is a perspective view of the cartridge table 316 having the flange 316C on which the suspension jig 335 is mounted.

As shown in FIGS. 15A and 15B, the top ring 301 is connected to a top ring shaft 308, and has a resilient pad 302 made of polyurethane or the like on its lower surface. The semiconductor wafer 304 is held in contact with the resilient pad 302 while it is being polished. The top ring 301 has a cylindrical guide ring 303 on its outer circumferential edge for preventing the semiconductor wafer 304 from being detached from the lower surface of the top ring 301 while the semiconductor wafer 304 is being polished. The guide ring 303 is fixed to the top ring 301 to hold the semiconductor wafer 304 within the holding surface of the top ring 301 so that the semiconductor wafer 304 is not dislodged from the top ring 301 under frictional forces produced between the semiconductor wafer 304 and the fixed abrasive 315 while the semiconductor wafer 304 is being polished. Further, the top ring 301 is supported by the top ring shaft 308 through a spherical bearing 307 so that the top ring 301 is tiltable with respect to the shaft 308.

The semiconductor wafer 304 is held on the lower surface of the resilient pad 302 attached to the lower surface of the top ring 301, and is pressed by the top ring 301 against the fixed abrasive 315 on the cartridge table 316 fixed to the main table 305. The main table 305 and the top ring 301 are rotated in one direction independently of each other at respective predetermined rotational speeds, whereby the fixed abrasive 315 and the semiconductor wafer 304 cause relative motion for thereby polishing the semiconductor wafer 304. At this time, water or a chemical L is supplied from the liquid supply nozzle 310 onto the fixed abrasive 315.

The water or the chemical is supplied onto the polishing surface of the fixed abrasive 315 in order to lubricate the polishing surface when the semiconductor wafer 304 is polished and also to cool the polishing surface for thereby removing heat generated when the semiconductor wafer 304 is polished. In an example, water is supplied at a rate of about 200 ml/min to the polishing surface on the fixed abrasive 315. The water may comprise ultrapure water free of impurities. A chemical such as an acid or alkali solution may be supplied instead of water.

The semiconductor wafer 304 is rotated by the drive shaft 308 in the direction indicated by the arrow X1 while being pressed against the fixed abrasive 315 through the resilient pad 302 by the top ring 301. The main table 305 to which the cartridge table 316 having the fixed abrasive 315 attached thereto is fixed is also rotated in the direction indicated by the arrow X2 independently of the semiconductor wafer 304. The surface 304A, to be polished, of the semiconductor wafer 304 is now polished by being brought into sliding contact with the surface 315A of the fixed abrasive 315.

The fixed abrasive 315 comprises a grindstone having a self-stop function which does not polish the surface 304A after surface irregularities of the surface 304A have been planarized by the polishing action thereof. The fixed abrasive 315 comprises abrasive particles of cerium oxide (CeO₂) or the like having an average particle diameter of 2 μm or less, and a binder of a synthetic resin such as polyimide or the like. The abrasive particles may alternatively be made of SiO₂, Al₂O₃, ZrO₂, MnO₂, Mn₂O₃, TiO₂, or the like. The binder may alternatively be phenolic resin, urethane resin, epoxy resin, polyvinyl alcohol resin, acrylic resin, or the like. As materials for the abrasive particles and the binder, suitable materials are selected from the above materials in view of the type of films formed on the semiconductor wafer to be polished and the affinity between the abrasive particles and the binder.

The semiconductor wafer 304 is polished under conditions of, for example, a wafer surface pressure of 3×10⁴ Pa (300 g/cm²), rotational speeds of 30 and 35 rpm for the table and the wafer, respectively, and a supply rate of 200 ml/min of pure water (containing 1 wt % or less of a surface active agent). Alternatively, the semiconductor wafer 304 may be polished under conditions of a wafer surface pressure of 5×10⁴ Pa (500 g/cm²), rotational speeds of 25 and 10 rpm for the table and the wafer, respectively, and a supply rate of 200 ml/min of pure water (containing 1 wt. % or less of a surface active agent).

A process of mounting the cartridge table 316 with the fixed abrasive 315 attached thereto on the main table 305 will be described below with reference to FIGS. 18A, 18B, 19A, 19B and 21. The cartridge table 316, immediately after it is placed on the main table 305, has the suspension jig 335 mounted on the flange 316C. At this time, the ball bearings 324 are not normally positioned in the recesses 333. The cartridge table 316 is moved on and along the surface 305A of the main table 305 so as to bring the center C1 of the cartridge table 316 into alignment with the center C2 of the main table 305. Since the ball bearings 324 roll while the cartridge table 316 is being moved on and along the surface 305A of the main table 305, the cartridge table 316 can easily be moved manually. Then, the cartridge table 316 is turned on the surface 305A to position the ball bearings 324 in the respective recesses 333 to bring the reverse surface 316B and the surface 305A into intimate contact with each other. At this time, since the ball bearings 324 roll while the cartridge table 316 is being turned on the surface 305A of the main table 305, the cartridge table 316 can easily be moved manually on and along the surface 305A. Thus, after the cartridge table 316 is placed on the main table 305, because the cartridge table 316 can easily be moved manually on the main table 305, the fixed abrasive 315 can be handled with ease, and can be easily positioned with respect to the main table 305.

Then, the hexagon socket head cap bolts 339 by which the suspension jig 335 is attached to the flange 316C of the cartridge table 316 are removed, and hence the suspension jig 335 is detached from the flange 316C. The clamp members 318 are attached to the flange 316C of the cartridge table 316, and fastened to the main table 305 by the bolts 319. In this manner, the process of mounting the cartridge table 316 on the main table 305 is completed.

Next, a process of removing the cartridge table 316 from the main table 305 will be described below. The bolts 319 are removed from the clamp members 318, and hence the clamp members 318 are detached from the flange 316C. The pusher bolts 331 are screwed into the internally threaded holes 330 in the projections 329 to cause the tip ends 331A of the pusher bolts 331 to engage the bottoms 342A of the grooves 342, thereby removing the cartridge table 316 from the main table 305. After the pusher bolts 331 are removed, the suspension jig 335 is placed on the flange 316C of the cartridge table 316. Then, the suspension jig 335 is positionally adjusted to align the internally threaded holes 338 of the suspension jig 335 with the internally threaded holes 334. Thereafter, the hexagon socket head cap bolts 339 are screwed into the internally threaded holes 338 and 334 to fasten the suspension jig 335 to the flange 316C of the cartridge table 316. A process of suspending the cartridge table 316 with the suspension jig 335 will be described later on.

A cartridge table 516 and a main table 505 of a polishing apparatus 403 according to a ninth embodiment of the present invention will be described below with reference to FIGS. 23A and 23B. Differences between the cartridge table 516 and the main table 505 of the polishing apparatus 403 in the ninth embodiment and the cartridge table 316 and the main table 305 of the polishing apparatus 401 in the eighth embodiment will be described below.

The cartridge table 516 incorporates a bearing member 522 disposed centrally in a reverse surface 516B thereof. The bearing member 522 comprises a holder 523, a ball bearing 524, and a bearing retainer plate, and the like. The main table 505 has a recess 533 formed therein which is disposed centrally in a surface 505A thereof.

According to the polishing apparatus 403 of the present embodiment, the cartridge table 516 with a fixed abrasive 515 attached thereto is placed on the surface 505A of the main table 505. Thereafter, the center of the cartridge table 516 is aligned with the center of the main table 505 for thereby placing the ball bearing 524 in the recess 533, so that the cartridge table 516 is positioned with respect to the main table 505. It is therefore not necessary to angularly align the cartridge table 516 with the main table 505 for positioning of the cartridge table 516 with respect to the main table 505.

When the cartridge table 516 is placed on the main table 505, because only one bearing 524 is used, the bearing 524 is normally brought into contact with the surface 505A, and a point on the outer edge of the reverse surface 516B contacts the surface 505A. A reaction force which the bearing 524 receives from the surface 505A is much greater than a reaction force which the point on the outer edge of the reverse surface 516B receives. Therefore, the resistance due to friction at the point is small, and hence the cartridge table 516 can be easily moved manually on the main table 505.

A cartridge table 616 and a main table 605 of a polishing apparatus 404 according to a tenth embodiment of the present invention will be described below with reference to FIGS. 24A, 24B, 25A and 25B. Differences between the cartridge table 616 and the main table 605 of the polishing apparatus 404 and the cartridge table 516 and the main table 505 of the polishing apparatus 403 shown in FIGS. 23A and 23B will be described below.

The cartridge table 616 has on a reverse surface 616B thereof a ridge 643 in the form of a rectangular parallelepiped, and the ridge 643 has a height h1 from the reverse surface 616B. The ridge 643 extends in the radial direction of the cartridge table 616. The height h1 is smaller than a downward projecting distance h2 of a bearing 624 from a surface 605A of the main table 605. The surface 605A has a groove 644 formed therein as a directional member in which the ridge 643 enters. The groove 644 extends in the radial direction of the main table 605, and has such a width that the bearing 624 enters in the groove 644 with a small play.

Since the height h1 of the ridge 643 is smaller than the projecting distance h2 of the bearing 624, when the cartridge table 616 is placed on the main table 605, the bearing 624 and a point on the outer edge of the reverse surface 616B (or a point on the ridge 643) normally contact the surface 605A. A reaction force which the bearing 624 receives from the surface 605A is much greater than a reaction force which the above point receives. Therefore, the cartridge table 616 can easily be moved manually on the main table 605. The main table 605 has a recess 633 which is disposed centrally in the surface 605A of the main table 605. The recess 633 has a depth h4 and the groove 644 has a depth h3, and the depth h4 is greater than the depth h3. The recess 633 is located adjacent to an end 644B of the groove 644 which is opposite to an end 644A located at the outer edge of the surface 605A. When the bearing 624 enters the recess 633, the bearing 624 also enters the end 644B of the groove 644.

The cartridge table 616 is placed on the main table 605, and the center of the cartridge table 616 is aligned with the center of the main table 605. The bearing 624 enters the recess 633 and the ridge 643 enters the groove 644, thus positioning the cartridge table 616 with respect to the main table 605. At this time, if the bearing 624 initially enters the recess 633, then the cartridge table 616 is turned to angularly align itself with the main table 605, whereby the ridge 643 is brought into the groove 644 to position the cartridge table 616 with respect to the main table 605.

If the bearing 624 initially enters the groove 644, then the bearing 624 is moved on the bottom of the groove 644 toward the recess 633 to directionally align the cartridge table 616 with the main table 605. After the bearing 624 reaches the recess 633, the cartridge table 616 is turned to angularly align itself with the main table 605 for thereby bringing the ridge 643 into the groove 644, thus positioning the cartridge table 616 with respect to the main table 605. Alternatively, the cartridge table 616 may first be angularly aligned and then directionally aligned with the main table 605.

According to the present embodiment, the bearing 624 and the ridge 643 allow the cartridge table 616 to be positioned accurately with respect to the main table 605, and also prevent the cartridge table 616 and the main table 605 from rotating relatively to each other. If the cartridge table 616 is fastened to the main table 605 by the clamp members 318 (see FIG. 16A), then the cartridge table 616 and the main table 605 are reliably prevented from rotating relatively to each other. A plurality of ridges 643 having a rectangular parallelepiped shape, and a plurality of grooves 644 for accommodating the ridges 643 may be provided radially at equal angular intervals around the recess 633. The width of the groove 644 may be smaller than the outside diameter (2R₁) of an inlet area of the recess 633 to allow the bearing 624 to roll on two parallel edges which are defined by boundaries of the groove 644 and the surface 605A. The cartridge table 616 may be positioned without the ridge 643.

FIG. 26 is a plan view of a polishing system 402 incorporating a polishing apparatus according to an embodiment of the present invention. The polishing system 402 has main tables 454 and 455, top rings 452 and 453, loading and unloading stages 422, a transport robot 424, and the like which are all placed on a base 471. The main tables 454 and 455 are identical in structure to the main table 305 (see FIGS. 15A and 15B). The cartridge table 316 (not shown in FIG. 26) with the fixed abrasive 315 (not shown in FIG. 26) is fixedly mounted on each of the main tables 454 and 455. The top rings 452 and 453 are identical in structure to the top ring 301 (see FIGS. 15A and 15B).

The polishing system 402 shown in FIG. 26 has four loading and unloading stages 422 for placing wafer cassettes 421 for storing a number of semiconductor wafers 304 (see FIGS. 15A and 15B). Each of the loading and unloading stages 422 may have a vertically movable mechanism. The transport robot 424 having two hands is disposed on a transport mechanism 423 so that the transport robot 424 can access the wafer cassettes 421 on the loading and unloading stages 422.

The lower one of the two hands of the transport robot 424 is used only to take out a semiconductor wafer 304 (see FIGS. 15A and 15B) from the wafer cassette 421, and the upper hand is used only to return a semiconductor wafer 304 into the wafer cassette 421. The two hands are arranged to position the clean semiconductor wafer which has been cleaned at an upper position for thereby preventing the cleaned semiconductor wafer from being further contaminated. The lower hand comprises a vacuum-attraction type hand for attracting a semiconductor wafer 304 under vacuum, and the upper hand comprises a drop-in type hand for holding a peripheral edge of a semiconductor wafer 304. The vacuum-attraction type hand can accurately transport a semiconductor wafer 304 irrespective of any displacement of the semiconductor wafer 304 in the wafer cassette 421. The drop-in type hand can transport a semiconductor wafer 304 while keeping the reverse surface clean because the drop-in type hand collects almost no dust unlike the vacuum-attraction type hand.

Two cleaning machines 425 and 426 are disposed in the opposite side of the wafer cassettes 421 with respect to the transport mechanism 423. Each of the cleaning machines 425 and 426 is located in a position that can be accessed by the hands of the transport robot 424. A wafer station 470 having four placement stages 427, 428, 429 and 430 for placing semiconductor wafers 304 (see FIGS. 15A and 15B) is disposed between the cleaning machines 425 and 426 at a position that can be accessed by the transport robot 424. The cleaning machines 425 and 426 have a spin-dry function for rotating semiconductor wafers 304 at a high speed and drying them. The cleaning machines 425 and 426 are capable of cleaning semiconductor wafers 304 in two-stage cleaning or three-stage cleaning without the need for a module replacement.

The cleaning machines 425 and 426 and the placement stages 427, 428, 429 and 430 are disposed in an area A_(B), and the wafer cassettes 421 and the transport robot 424 are disposed in an area A_(A). A partition wall 484 is disposed to provide different levels of cleanliness in the areas A_(A) and A_(B). The partition wall 484 has an opening at which a shutter 431 is provided for delivering semiconductor wafers 304 therethrough between the areas A_(A) and A_(B). A transport robot 480 having two hands is located in a position where the transport robot 480 can access the cleaning machine 425 and the three placement stages 427, 429 and 430, and a transport robot 481 having two hands is located in a position where the transport robot 481 can access the cleaning machine 426 and the three placement stages 428, 429 and 430.

The placement stage 427 is used to transfer semiconductor wafers 304 (see FIGS. 15A and 15B) between the transport robot 424 and the transport robot 480, and has a sensor 491 for detecting whether there is a semiconductor wafer 304 or not. The placement stage 428 is used to transfer semiconductor wafers 304 between the transport robot 424 and the transport robot 481, and has a sensor 492 for detecting whether there is a semiconductor wafer 304 or not. The placement stage 429 is used to deliver semiconductor wafers 304 from the transport robot 481 to the transport robot 480, and has a sensor 493 for detecting whether there is a semiconductor wafer 304 or not, and a rinse nozzle 495 for either preventing semiconductor wafers 304 from being dried or rinsing semiconductor wafers 304. The placement stage 430 is used to deliver semiconductor wafers 304 from the transport robot 480 to the transport robot 481, and has a sensor 494 for detecting whether there is a semiconductor wafer 403 or not, and a rinse nozzle 496 for either preventing semiconductor wafers 304 from being dried or rinsing semiconductor wafers 304.

The placement stages 429 and 430 are disposed in a common water-resistant cover, and a shutter 497 is provided at an opening of the cover which allows semiconductor wafers to be delivered therethrough. The placement stage 429 is disposed above the placement stage 430. A semiconductor wafer 304 which has been cleaned is placed on the placement stage 429, and a semiconductor wafer 304 to be cleaned is placed on the placement stage 430, thereby preventing the semiconductor wafers from being contaminated due to droplets of rinsing water. In FIG. 26, the sensors 491, 492, 493 and 494, the rinse nozzles 495 and 496, and the shutter 497 are schematically shown, and their positions and shapes are not accurately shown.

The upper hands of the transport robot 480 and the transport robot 481 are used to deliver semiconductor wafers 304 which have been cleaned once to the cleaning machines 425, 426, 482 and 483 or the placement stages in the wafer station 470. The lower hands of the transport robot 480 and the transport robot 481 are used to deliver semiconductor wafers 304 which have never been cleaned, and semiconductor wafers 304 to be polished. The lower hands are used to transfer semiconductor wafers 304 to and from a reversing machine for thereby preventing the upper hands from being contaminated by droplets of the rinsing water from an upper wall of the reversing machine.

The cleaning machine 482 is disposed so as to be adjacent to the cleaning machine 425 in a position that is accessible by the hand of the transport robot 480. The cleaning machine 483 is disposed so as to be adjacent to the cleaning machine 426 in a position that is accessible by the hand of the transport robot 481.

The cleaning machines 425, 426, 482 and 483, the placement stages 427, 428, 429 and 430 in the wafer station 470, and the transport robots 480 and 481 are disposed in the area A_(B). The air pressure in the area A_(B) is adjusted so as to be lower than the air pressure in the area A_(A). The cleaning machines 482 and 483 are capable of cleaning both sides of semiconductor wafers 304.

The polishing system 402 has a housing 466 so as to enclose the constituent units or components thereof. The interior of the housing 466 is divided into a plurality of chambers (including the areas A_(A) and A_(B)) by the partition wall 484 and partition walls 485, 486, 487 and 467. A polishing chamber separate from the area A_(B) is defined by the partition wall 487, and the polishing chamber is divided into two areas A_(C) and A_(D) by the partition wall 467. In each of the two areas A_(C) and A_(D) there are provided two main tables and a top ring for holding one semiconductor wafer 304 (see FIGS. 15A and 15B) and pressing the semiconductor wafer 304 against the main table to polish the semiconductor wafer 304.

Specifically, in the area A_(C), there are provided the main tables 454 and 456 and the top ring 452, and in the area A_(D), there are provided the main tables 455 and 457 and the top ring 453. In the area A_(C), there are provided a polishing liquid nozzle 460 for supplying a polishing liquid to the main table 454, and a dresser 458 for dressing the main table 454.

In the area A_(D), there are provided a polishing liquid nozzle 461 for supplying a polishing liquid to the main table 455, and a dresser 459 for dressing the main table 455. A dresser 468 for dressing the main table 456 is disposed in the area A_(C), and a dresser 469 for dressing the main table 457 is disposed in the area A_(D). Wet-type wafer thickness measuring devices may be installed in place of the respective main tables 456 and 457. The wet-type wafer thickness measuring devices are capable of measuring the thickness of a film of a semiconductor wafer 304 immediately after it has been polished, and allow the semiconductor wafer 304 to be additionally polished. Further, a polishing process of a next semiconductor wafer 304 can be controlled based on the measured values by the thickness measuring devices.

Semiconductor wafers 304 (see FIGS. 15A and 15B) which have been transferred to the respective top rings 452 and 453 are held under vacuum by vacuum attraction mechanisms of the top rings 452 and 453, and delivered to the main tables 454 and 455, respectively. Then, the semiconductor wafers 304 are polished by the polishing surfaces of the fixed abrasives 315 (see FIGS. 15A and 15B) attached to the cartridge tables 316 (see FIGS. 15A and 15B) which are mounted on the respective main tables 454 and 455. By polishing the semiconductor wafers 304 using the cartridge tables 316 with the fixed abrasive 315 attached thereto, excellent polished surfaces having no scratches or less scratch can be obtained even in a one-stage polishing process. The main tables 456 and 457 are disposed in respective positions that can be accessed by the respective top rings 452 and 453. After the semiconductor wafers 304 have been polished by the main tables 454 and 455, the semiconductor wafers 304 are polished in a finish-polishing manner by respective finish polishing pads (not shown) attached to the respective main tables 456 and 457. On the finish main tables 456 and 457, there are provided the polishing pads such as SUBA 400 or Polytex (both manufactured by Rodel Nitta Co.). Thus, while either pure water or a chemical free of abrasive particles is supplied to the polishing pads, the semiconductor wafers 304 are finished (polished or cleaned). Alternatively, the semiconductor wafers 304 are polished by supplying a slurry containing abrasive particles.

The polishing system 402 also has a hand lifter 501 (see FIG. 27) as a carrier device. The cartridge table 316 (see FIGS. 15A and 15B) having the fixed abrasive 315 (see FIGS. 15A and 15B) attached thereto is delivered to the polishing system 402 by the hand lifter 501 in such a state that the suspension jig 335 (see FIG. 21) is mounted on the flange 316C (see FIGS. 15A and 15B), and the cartridge table 316 and the suspension jig 335 are placed on the main table 454 or 455.

A structure of the hand lifter 501 serving as a carrier device for delivering the cartridge table 316 suspended by the suspension jig 335 will be described below with reference to FIG. 27.

The hand lifter 501 comprises a horizontal base 502, wheels 503 mounted on the base 502, a lifter body 504 connected to one end of the base 502 and extending vertically from the base 502, and two suspension bars 507 vertically movable along the lifter body 504. The two suspension bars 507 extend horizontally and are parallel to each other. The hand lifter 501 has a hand wheel (not shown) for vertically moving the suspension bars 507 along the lifter body 504. When the hand wheel is manually turned in a given direction, the two suspension bars 507 are vertically moved along the lifter body 504. Since the hand lifter 501 has the wheels 503, the hand lifter 501 can be manually moved in the direction indicated by the arrow P1 toward the polishing system 402 on a floor 506 on which the polishing system 402 is installed.

As shown in FIG. 27, the two suspension bars 507 sandwich the shaft 341 of the suspension jig 335, and lift the flange 337 to elevate the cartridge table 316. The elevated cartridge table 316 is kept in a horizontal posture. The hand lifter 501 can lift the cartridge table 316 to a position higher than the main table 454 and also higher than the main table 455 (not shown in FIG. 27).

The hand lifter 501 which has lifted the cartridge table 316 moves in the direction indicated by the arrow P1, approaches the polishing system 402, and the base 502 of the hand lifter 501 enters a cavity 472 defined as a space in a side 471A of the base 471 of the polishing system 402 (see FIGS. 26 and 27). The cavity 472 has an upper surface 473 spaced upwardly from the floor 506 by a distance between 50 mm and 80 mm.

As shown in FIG. 28, when the base 502 further enters the cavity 472 (utility space), and the cartridge table 316 suspended by the suspension bars 507 comes to a position substantially directly above the main table 454, the non-illustrated hand wheel is turned in a direction opposite to the above given direction to lower the suspension bars 507 in the direction indicated by the arrow Q1. Then, the cartridge table 316 is placed on the main table 454, and the suspension bars 507 disengage from the flange 337. Thereafter, the hand lifter 501 is moved in a direction opposite to the direction indicated by the arrow P1 (see FIG. 27) so as to be away from the polishing system 402.

Thereafter, as described above, the cartridge table 316 is manually moved on the main table 454 until the bearings 324 (see FIGS. 18A and 18B) incorporated in the cartridge table 316 enter the recesses 333 (see FIGS. 19A and 19B) in the main table 454, thus positioning the cartridge table 316 with respect to the main table 454. Then, the suspension jig 335 is removed from the flange 316C of the cartridge table 316, and carried out of the polishing system 402 by the hand lifter 501. The cartridge table 316 from which the suspension jig 335 is removed is fastened to the main table 454 by the clamp members 318 (see FIG. 16A) through the bolts 319 (see FIG. 16A). The setup of the fixed abrasive 315 (see FIG. 16A) on the main table 454 is now finished.

In the case where the cartridge table 316 is removed from the main table 454, the bolts 319 are loosened and the clamp members 318 are detached, and then the suspension jig 335 is carried from the outside of the polishing system 402 to a position over the main table 454 by the hand lifter 501. After the suspension jig 335 is attached to the flange 316C of the cartridge table 316 as described above, the hand lifter 501 with the suspension bars 507 positioned lower than the flange 337 approaches the cartridge table 316. When the base 502 enters the cavity 472 and the tip ends of the suspension bars 507 reach a position directly below the flange 337, the hand lifter 501 stops. The non-illustrated hand wheel is turned in the given direction to lift the suspension bars 507. Thus, the tip ends of the suspension bars 507 are brought into contact with the flange 337, thus lifting the cartridge table 316. The bearings 324 are positioned above the surface 454A of the main table 454 and are brought out of the recesses 333. The hand lifter 501 is moved in the direction opposite to the direction indicated by the arrow P1 (see FIG. 27). The removal of the cartridge table 316 from the main table 454 is now completed.

According to the polishing system 402 of the present embodiment, the cartridge table 316 with the fixed abrasive 315 attached thereto can manually be moved and placed on the main table 454 by the hand lifter 501. The cartridge table 316 can manually be moved over the main table 454 to put the bearings 324 (see FIGS. 18A and 18B) into the recesses 333 (see FIGS. 18A, 18B, and 19A, 19B), can be positioned on the main table 454, and can be fastened to the main table 454. Therefore, it is not necessary to provide any parts on the main table 454 for positioning the cartridge table 316 on the main table 454.

The cartridge table 316 can manually be lifted and removed from the main table 454 by the hand lifter 501. The cartridge table 316 with the fixed abrasive 315 attached thereto can thus be handled with ease. Because the cartridge table 316 with the heavy fixed abrasive 315 attached thereto can be carried, lifted, or lowered by the hand lifter 501, the safety of the operator can be ensured. Even if the cartridge table 316 with the fixed abrasive 315 attached thereto is heavy, the cartridge table 316 can manually be handled without its handling capability being affected. Therefore, the fixed abrasive 315 can sufficiently be increased in thickness, and hence the service life of the fixed abrasive 315 can be prolonged.

As shown in FIG. 26, a cavity 472 is also defined in an upper side 471B of the base 471 in the polishing system 402. In the case where the cartridge table 316 is placed on the main table 455, the hand lifter 501 is moved upwardly in FIG. 26. The cartridge table 316 can thus be placed on the main table 455 in the same manner as it is placed on the main table 454.

The hand lifter 501 may be replaced with a crane device as a carrier device. The crane device may be an industrial machine such as a crane, a chain block, a hoist, or the like for suspending an object with a wire. If a crane arm, a crane body, a lifter, and the like are incorporated in advance in the base 471 of the polishing system 402 or are easily detachably combined with the base 471, then the cavity 472 does not need to be formed in the base 471 of the polishing system 402, and the crane device may be used to replace the main tables 454 and 455 with new ones. With this arrangement, the possibility of bringing particles from the exterior space into the polishing system is reduced to thus allow operations to be made in a clean environment. If the crane device is used, then the suspension jig 335 does not need the flange 337, but may have at least one member, preferably three members such as the pusher bolts 331 (see FIG. 16A) for hitching the suspension wire. Although the bearings 324 are illustrated as ball bearings in the embodiments, they may be air bearings or linear bearings (linear guides). The crane device is effective to mount a large-size cartridge table or a heavy cartridge table with a fixed abrasive or a polishing pad attached thereto on the main table.

As shown in FIG. 29A, a polishing system 405 may have a rail 702, and a built-in crane device 701 (partly shown) suspended from the rail 702 and movable along the rail 702. The polishing system 405 is different from the polishing system 402 in that the cavity 472 is eliminated and the crane device 701 and the rail 702 are added.

The crane device 701 includes a moving unit 703, a take-up unit 704, a rope 707, and a hook 706. The moving unit 703 engages the rail 702 and moves horizontally along the rail 702 in the direction indicated by the arrow P2 or the direction opposite to the direction indicated by the arrow P2. The take-up unit 704 is mounted on the moving unit 703, and winds or unwinds the rope 707. The hook 706 is connected to the end of the rope 707. The hook 706 is lifted in the direction opposite to the direction indicated by the arrow Q2 (see FIG. 29C) when the rope 707 is wound by the take-up unit 704, and lowered in the direction indicated by the arrow Q2 when the rope 707 is unwound from the take-up unit 704.

The polishing system 405 also has a suspension jig 735, a cartridge table 716, and a main table 705. The rail 702 is mounted on a ceiling 405A of the polishing system 405, and permits the crane device 701 to move from the side 405B of the polishing system 405 to at least a position directly above the main table 705. For moving the cartridge table 716 onto the main table 705, the suspension jig 735 is fastened to the cartridge table 716 by hexagon socket head cap bolts 739. Then, the hook 706 engages a flange 737 of the suspension jig 735 attached to the cartridge table 716. Thereafter, the take-up unit 704 winds the rope 707 to lift the hook 706, and hence the cartridge table 716 is suspended by the crane device 701.

Then, as shown in FIG. 29B, the moving unit 703 moves along the rail 702 in the direction indicated by the arrow P2, and the cartridge table 716 is carried to a position above a surface 705A of the main table 705.

Next, as shown in FIG. 29C, the take-up unit 704 unwinds the rope 707 to lower the hook 706 in the direction indicated by the arrow Q2, and hence the cartridge table 716 is placed on the surface 705A of the main table 705.

After the cartridge table 716 is placed on the main table 705, the hexagon socket head cap bolts 739 are removed, and the suspension jig 735 is detached from the cartridge table 716. The suspension jig 735 is suspended by the crane device 701, and carried out of the polishing system 405 in the direction opposite to the direction indicated by the arrow P2.

Because the polishing system 405 has the crane device 701, the handling of the cartridge table 716 can be improved and the safety of the operator can be improved. The cartridge table 716 can be made heavy, the fixed abrasive (see FIGS. 15A and 15B) can be sufficiently thick, and the service life of the fixed abrasive can be prolonged. Since the crane device 701 is of the built-in type, it is not necessary to provide a wide area outside of the polishing system 405 for placing the crane device 701 laterally of the polishing system 405, and hence any working zone for maintenance can be reduced.

As shown in FIG. 30, a crane device 801 may have an eye bolt 837 attached to a suspension jig 835 instead of the flange for suspending the suspension jig 835. With this arrangement, the crane device 801 does not require a hook and can be compact.

The embodiments described above are only preferred embodiments of the present invention, and various changes and modifications may be made therein without departing from the scope of the invention.

According to the present invention, as described above, since the moving mechanism and the positioning member are provided, the cartridge table can be moved easily on the main table by the moving mechanism, and can be positioned with respect to the main table by the positioning member. The polishing tool can thus be handled with ease, and the safety of the operator can be increased. Further, the polishing tool can be increased in thickness for a longer service life.

Industrial Applicability

The present invention is applicable to a polishing apparatus having a polishing tool for polishing a workpiece such as a semiconductor wafer to a flat mirror finish. 

1. A polishing apparatus for polishing a workpiece, comprising: a table; a base placed on said table; and a polishing tool fixed to said base and having a polishing surface for polishing a surface of the workpiece; wherein said base has at least a portion which is not fixed to said table for allowing said base to be deformed through said portion.
 2. A polishing apparatus according to claim 1, further comprising a fixing member for fixing said base to said table.
 3. A polishing apparatus according to claim 1, further comprising: a transmission member provided on said table at a position where said base is not fixed to said table; wherein said table makes a motion, and the motion of said table is transmitted to said base through said transmission member.
 4. A polishing apparatus according to claim 1, wherein said base comprises a plurality of base segments.
 5. A polishing apparatus according to claim 1, wherein said polishing tool comprises a fixed abrasive.
 6. A polishing apparatus according to claim 1, wherein said base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times a coefficient of linear expansion of said polishing tool.
 7. A polishing apparatus for polishing a workpiece, comprising: a table; a base placed on said table and having an annular shape; a polishing tool fixed to said base and having a polishing surface for polishing a surface of the workpiece; and a fixing member for fixing said base to said table; wherein an inner circumferential portion of said base is fixed to said table by said fixing member and an outer circumferential portion of said base is not fixed to said table so as to allow said base to be deformed radially outwardly.
 8. A polishing apparatus according to claim 7, wherein said base comprises a plurality of base segments having a fan shape.
 9. A polishing apparatus according to claim 7, further comprising: a plurality of transmission members provided along a circumferential direction of said table; and a plurality of holes formed in said base and having an elongate shape extending in the radial direction of said base, said transmission members being inserted into said holes, respectively, for transmitting the motion of said table to said base.
 10. A polishing apparatus for polishing a workpiece, comprising: a table; a base placed on said table and having an annular shape; a polishing tool fixed to said base and having a polishing surface for polishing a surface of the workpiece; and a fixing member for fixing said base to said table; wherein said base comprises a plurality of base segments, said polishing tool comprises a plurality of polishing tool segments which are fixed to said plurality of base segments, respectively, and an outer circumferential portion of said base is fixed to said table by said fixing member and an inner circumferential portion of said base is not fixed to said table so as to allow said base to be deformed radially inwardly.
 11. A polishing apparatus according to claim 10, wherein each of said base segments has a fan shape.
 12. A polishing apparatus according to claim 10, further comprising: a plurality of transmission members provided along a circumferential direction of said table; and a plurality of holes formed in said base and having an elongate shape extending in the radial direction of said base, said transmission members being inserted into said holes, respectively, for transmitting the motion of said table to said base.
 13. A polishing apparatus for polishing a workpiece, comprising: a table which makes a motion; a base placed on said table; a polishing tool fixed to said base and having a polishing surface for polishing a surface of the workpiece; a plurality of transmission members provided along a circumferential direction of said table; and a plurality of holes formed in said base and having an elongate shape extending in the radial direction of said base, said transmission members being inserted into said holes, respectively, for transmitting the motion of said table to said base.
 14. A polishing tool assembly for polishing a workpiece, comprising: a base positionable on a table; a polishing tool fixed to said base and having a polishing surface for polishing a surface of the workpiece, said polishing tool comprising a fixed abrasive; and a plurality of holes formed in said base and having an elongate shape extending in the radial direction of said base; wherein said holes are arranged to allow a plurality of transmission members provided along a circumferential direction of said table to be inserted therein when said polishing tool assembly is mounted on said table.
 15. A polishing tool assembly for polishing a workpiece, comprising: a plurality of polishing tool segments having a polishing surface for polishing a surface of the workpiece; and a polishing tool attachment for holding said polishing tool segments thereon in such a state that the circumferentially adjacent polishing tool segments are held in close contact with each other.
 16. A polishing tool assembly according to claim 15, wherein said polishing tool segment comprises a fixed abrasive having abrasive particles fixed by a binder.
 17. A polishing tool assembly according to claim 15, wherein each of said polishing tool segments is in a sectorial or fan-shaped form, and said circumferentially adjacent polishing tool segments are held in close contact with each other to form a disk or cylindrical shape as a whole.
 18. A polishing tool assembly according to claim 17, wherein said polishing tool segments are mounted on said polishing tool attachment in such a state that said polishing tool segments are positioned with use of a positioning member mounted around the outer circumferential edges of said polishing tool segments.
 19. A polishing tool assembly according to claim 17, wherein said polishing tool attachment has an outside diameter larger than said polishing tool segments.
 20. A polishing tool assembly according to claim 15, wherein said polishing tool segments are mounted on a single polishing tool attachment.
 21. A polishing tool according to claim 15, wherein said polishing tool attachment is divided into a plurality of attachment segments so as to correspond to said polishing tool segments, and said polishing tool segments are mounted on the respective attachment segments.
 22. A polishing apparatus for polishing a workpiece, comprising: a workpiece holding device for holding the workpiece; a polishing tool assembly according to claim 15; and a polishing table on which said polishing tool is mounted.
 23. A polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which said polishing tool is mounted; a main table disposed so as to face a reverse surface of said cartridge table and having a support surface for supporting said cartridge table thereon; a moving mechanism mounted on said reverse surface of said cartridge table or said support surface of said main table for facilitating movement of said cartridge table along said main table; and a positioning member for positioning said cartridge table with respect to said main table.
 24. A polishing apparatus according to claim 23, wherein said moving mechanism comprises a rolling element which rolls on said support surface of said main table, or said reverse surface of said cartridge table.
 25. A polishing apparatus according to claim 24, wherein said positioning member comprises a recess formed in said support surface of said main table or said reverse surface of said cartridge table for accommodating said rolling element.
 26. A polishing apparatus according to claim 23, further comprising a fastening member for securing said cartridge table to said main table.
 27. A polishing apparatus according to claim 23, wherein said moving mechanism is disposed in point symmetry with respect to a center of the surface on which said moving mechanism is mounted.
 28. A polishing apparatus according to claim 23, wherein said polishing tool comprises a fixed abrasive.
 29. A polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which said polishing tool is mounted; a main table disposed so as to face a reverse surface of said cartridge table and having a support surface for supporting said cartridge table thereon; a rolling element mounted on said reverse surface of said cartridge table or said support surface of said main table and rolling on said support surface of said main table or said reverse surface of said cartridge table; and a recess formed in said support surface of said main table or said reverse surface of said cartridge table for accommodating said rolling element.
 30. A polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which said polishing tool is mounted; and a main table disposed so as to face a reverse surface of said cartridge table and having a support surface for supporting said cartridge table thereon; wherein said cartridge table is coupled to a carrier device for carrying said cartridge table onto said support surface of said main table when said cartridge table is to be mounted on said main table and carrying said cartridge table upwardly above said support surface when said cartridge table is dismounted from said main table.
 31. A polishing apparatus according to claim 30, further comprising a jig attached to said cartridge table and having a coupling member through which said cartridge table is coupled to said carrier device.
 32. A polishing apparatus according to claim 30, wherein said polishing apparatus has a space to allow said carrier device to access said main table.
 33. A polishing apparatus according to claim 30, further comprising a fastening member for securing said cartridge table to said main table.
 34. A method of assembling a cartridge table, comprising: preparing a cartridge table having a surface on which a polishing tool is mounted, said polishing tool having a polishing surface for polishing a surface of a workpiece; attaching a jig having a coupling member to said cartridge table; coupling said jig attached to said cartridge table through said coupling member to a carrier device; carrying said cartridge table to a position above a support surface of a main table for supporting said cartridge table by said carrier device, and lowering said cartridge table to place said cartridge table onto said support surface by said carrier device; removing said jig from said cartridge table; moving said cartridge table along said support surface of said main table by a moving mechanism which is mounted on a reverse surface of said cartridge table or said support surface of said main table; and positioning said cartridge table with respect to said main table by a positioning member.
 35. A method according to claim 34, wherein said moving mechanism comprises a rolling element which rolls on said support surface of said main table or said reverse surface of said cartridge table.
 36. A method according to claim 35, wherein said positioning member comprises a recess, and said positioning is performed by accommodating said rolling element into said recess. 